Merge pull request #86 from tsoding/simd

SIMD rendering

Makefile

@@ -1,11 +1,13 @@
+# TODO(#87): we need an option to build with system libraries
 VODUS_PKGS=freetype2
-VODUS_CXXFLAGS=-Wall -fno-exceptions -std=c++17 -ggdb `pkg-config --cflags $(VODUS_PKGS)` -I./third_party/ffmpeg-4.3-dist/usr/local/include/ -I./third_party/giflib-5.2.1-dist/usr/local/include/
+VODUS_CXXFLAGS=-Wall -fno-exceptions -std=c++17 -msse4 -ggdb `pkg-config --cflags $(VODUS_PKGS)` -I./third_party/ffmpeg-4.3-dist/usr/local/include/ -I./third_party/giflib-5.2.1-dist/usr/local/include/
 VODUS_LIBS=`pkg-config --libs $(VODUS_PKGS)` -L./third_party/giflib-5.2.1-dist/usr/local/lib/ -l:libgif.a -L./third_party/ffmpeg-4.3-dist/usr/local/lib/ -lavcodec -lavutil -lswresample -pthread -lm -llzma -lz
 
 EMOTE_DOWNLOADER_PKGS=libcurl
 EMOTE_DOWNLOADER_CXXFLAGS=-Wall -fno-exceptions -std=c++17 -ggdb `pkg-config --cflags $(EMOTE_DOWNLOADER_PKGS)`
 EMOTE_DOWNLOADER_LIBS=`pkg-config --libs $(EMOTE_DOWNLOADER_PKGS)`
 
+# TODO(#88): render config file
 RENDER_ARGS=--font assets/ComicNeue_Bold.otf --output output.mpeg --font-size 46 --fps 30 --width 704 --height 576 --limit 20 sample.txt --bitrate 6000000
 
 .PHONY: all

src/stb_image.h

@@ -1177,7 +1177,7 @@ static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x,
       ri.bits_per_channel = 8;
    }
 
-   // @TODO: move stbi__convert_format to here
+   // @todo: move stbi__convert_format to here
 
    if (stbi__vertically_flip_on_load) {
       int channels = req_comp ? req_comp : *comp;
@@ -1201,8 +1201,8 @@ static stbi__uint16 *stbi__load_and_postprocess_16bit(stbi__context *s, int *x,
       ri.bits_per_channel = 16;
    }
 
-   // @TODO: move stbi__convert_format16 to here
-   // @TODO: special case RGB-to-Y (and RGBA-to-YA) for 8-bit-to-16-bit case to keep more precision
+   // @todo: move stbi__convert_format16 to here
+   // @todo: special case RGB-to-Y (and RGBA-to-YA) for 8-bit-to-16-bit case to keep more precision
 
    if (stbi__vertically_flip_on_load) {
       int channels = req_comp ? req_comp : *comp;
@@ -5640,8 +5640,8 @@ static void *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int req
    int RLE_repeating = 0;
    int read_next_pixel = 1;
    STBI_NOTUSED(ri);
-   STBI_NOTUSED(tga_x_origin); // @TODO
-   STBI_NOTUSED(tga_y_origin); // @TODO
+   STBI_NOTUSED(tga_x_origin); // @todo
+   STBI_NOTUSED(tga_y_origin); // @todo
 
    //   do a tiny bit of precessing
    if ( tga_image_type >= 8 )

src/stb_image_resize.h

@@ -0,0 +1,2631 @@
+/* stb_image_resize - v0.96 - public domain image resizing
+   by Jorge L Rodriguez (@VinoBS) - 2014
+   http://github.com/nothings/stb
+
+   Written with emphasis on usability, portability, and efficiency. (No
+   SIMD or threads, so it be easily outperformed by libs that use those.)
+   Only scaling and translation is supported, no rotations or shears.
+   Easy API downsamples w/Mitchell filter, upsamples w/cubic interpolation.
+
+   COMPILING & LINKING
+      In one C/C++ file that #includes this file, do this:
+         #define STB_IMAGE_RESIZE_IMPLEMENTATION
+      before the #include. That will create the implementation in that file.
+
+   QUICKSTART
+      stbir_resize_uint8(      input_pixels , in_w , in_h , 0,
+                               output_pixels, out_w, out_h, 0, num_channels)
+      stbir_resize_float(...)
+      stbir_resize_uint8_srgb( input_pixels , in_w , in_h , 0,
+                               output_pixels, out_w, out_h, 0,
+                               num_channels , alpha_chan  , 0)
+      stbir_resize_uint8_srgb_edgemode(
+                               input_pixels , in_w , in_h , 0,
+                               output_pixels, out_w, out_h, 0,
+                               num_channels , alpha_chan  , 0, STBIR_EDGE_CLAMP)
+                                                            // WRAP/REFLECT/ZERO
+
+   FULL API
+      See the "header file" section of the source for API documentation.
+
+   ADDITIONAL DOCUMENTATION
+
+      SRGB & FLOATING POINT REPRESENTATION
+         The sRGB functions presume IEEE floating point. If you do not have
+         IEEE floating point, define STBIR_NON_IEEE_FLOAT. This will use
+         a slower implementation.
+
+      MEMORY ALLOCATION
+         The resize functions here perform a single memory allocation using
+         malloc. To control the memory allocation, before the #include that
+         triggers the implementation, do:
+
+            #define STBIR_MALLOC(size,context) ...
+            #define STBIR_FREE(ptr,context)   ...
+
+         Each resize function makes exactly one call to malloc/free, so to use
+         temp memory, store the temp memory in the context and return that.
+
+      ASSERT
+         Define STBIR_ASSERT(boolval) to override assert() and not use assert.h
+
+      OPTIMIZATION
+         Define STBIR_SATURATE_INT to compute clamp values in-range using
+         integer operations instead of float operations. This may be faster
+         on some platforms.
+
+      DEFAULT FILTERS
+         For functions which don't provide explicit control over what filters
+         to use, you can change the compile-time defaults with
+
+            #define STBIR_DEFAULT_FILTER_UPSAMPLE     STBIR_FILTER_something
+            #define STBIR_DEFAULT_FILTER_DOWNSAMPLE   STBIR_FILTER_something
+
+         See stbir_filter in the header-file section for the list of filters.
+
+      NEW FILTERS
+         A number of 1D filter kernels are used. For a list of
+         supported filters see the stbir_filter enum. To add a new filter,
+         write a filter function and add it to stbir__filter_info_table.
+
+      PROGRESS
+         For interactive use with slow resize operations, you can install
+         a progress-report callback:
+
+            #define STBIR_PROGRESS_REPORT(val)   some_func(val)
+
+         The parameter val is a float which goes from 0 to 1 as progress is made.
+
+         For example:
+
+            static void my_progress_report(float progress);
+            #define STBIR_PROGRESS_REPORT(val) my_progress_report(val)
+
+            #define STB_IMAGE_RESIZE_IMPLEMENTATION
+            #include "stb_image_resize.h"
+
+            static void my_progress_report(float progress)
+            {
+               printf("Progress: %f%%\n", progress*100);
+            }
+
+      MAX CHANNELS
+         If your image has more than 64 channels, define STBIR_MAX_CHANNELS
+         to the max you'll have.
+
+      ALPHA CHANNEL
+         Most of the resizing functions provide the ability to control how
+         the alpha channel of an image is processed. The important things
+         to know about this:
+
+         1. The best mathematically-behaved version of alpha to use is
+         called "premultiplied alpha", in which the other color channels
+         have had the alpha value multiplied in. If you use premultiplied
+         alpha, linear filtering (such as image resampling done by this
+         library, or performed in texture units on GPUs) does the "right
+         thing". While premultiplied alpha is standard in the movie CGI
+         industry, it is still uncommon in the videogame/real-time world.
+
+         If you linearly filter non-premultiplied alpha, strange effects
+         occur. (For example, the 50/50 average of 99% transparent bright green
+         and 1% transparent black produces 50% transparent dark green when
+         non-premultiplied, whereas premultiplied it produces 50%
+         transparent near-black. The former introduces green energy
+         that doesn't exist in the source image.)
+
+         2. Artists should not edit premultiplied-alpha images; artists
+         want non-premultiplied alpha images. Thus, art tools generally output
+         non-premultiplied alpha images.
+
+         3. You will get best results in most cases by converting images
+         to premultiplied alpha before processing them mathematically.
+
+         4. If you pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED, the
+         resizer does not do anything special for the alpha channel;
+         it is resampled identically to other channels. This produces
+         the correct results for premultiplied-alpha images, but produces
+         less-than-ideal results for non-premultiplied-alpha images.
+
+         5. If you do not pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED,
+         then the resizer weights the contribution of input pixels
+         based on their alpha values, or, equivalently, it multiplies
+         the alpha value into the color channels, resamples, then divides
+         by the resultant alpha value. Input pixels which have alpha=0 do
+         not contribute at all to output pixels unless _all_ of the input
+         pixels affecting that output pixel have alpha=0, in which case
+         the result for that pixel is the same as it would be without
+         STBIR_FLAG_ALPHA_PREMULTIPLIED. However, this is only true for
+         input images in integer formats. For input images in float format,
+         input pixels with alpha=0 have no effect, and output pixels
+         which have alpha=0 will be 0 in all channels. (For float images,
+         you can manually achieve the same result by adding a tiny epsilon
+         value to the alpha channel of every image, and then subtracting
+         or clamping it at the end.)
+
+         6. You can suppress the behavior described in #5 and make
+         all-0-alpha pixels have 0 in all channels by #defining
+         STBIR_NO_ALPHA_EPSILON.
+
+         7. You can separately control whether the alpha channel is
+         interpreted as linear or affected by the colorspace. By default
+         it is linear; you almost never want to apply the colorspace.
+         (For example, graphics hardware does not apply sRGB conversion
+         to the alpha channel.)
+
+   CONTRIBUTORS
+      Jorge L Rodriguez: Implementation
+      Sean Barrett: API design, optimizations
+      Aras Pranckevicius: bugfix
+      Nathan Reed: warning fixes
+
+   REVISIONS
+      0.97 (2020-02-02) fixed warning
+      0.96 (2019-03-04) fixed warnings
+      0.95 (2017-07-23) fixed warnings
+      0.94 (2017-03-18) fixed warnings
+      0.93 (2017-03-03) fixed bug with certain combinations of heights
+      0.92 (2017-01-02) fix integer overflow on large (>2GB) images
+      0.91 (2016-04-02) fix warnings; fix handling of subpixel regions
+      0.90 (2014-09-17) first released version
+
+   LICENSE
+     See end of file for license information.
+
+   TODO
+      Don't decode all of the image data when only processing a partial tile
+      Don't use full-width decode buffers when only processing a partial tile
+      When processing wide images, break processing into tiles so data fits in L1 cache
+      Installable filters?
+      Resize that respects alpha test coverage
+         (Reference code: FloatImage::alphaTestCoverage and FloatImage::scaleAlphaToCoverage:
+         https://code.google.com/p/nvidia-texture-tools/source/browse/trunk/src/nvimage/FloatImage.cpp )
+*/
+
+#ifndef STBIR_INCLUDE_STB_IMAGE_RESIZE_H
+#define STBIR_INCLUDE_STB_IMAGE_RESIZE_H
+
+#ifdef _MSC_VER
+typedef unsigned char  stbir_uint8;
+typedef unsigned short stbir_uint16;
+typedef unsigned int   stbir_uint32;
+#else
+#include <stdint.h>
+typedef uint8_t  stbir_uint8;
+typedef uint16_t stbir_uint16;
+typedef uint32_t stbir_uint32;
+#endif
+
+#ifndef STBIRDEF
+#ifdef STB_IMAGE_RESIZE_STATIC
+#define STBIRDEF static
+#else
+#ifdef __cplusplus
+#define STBIRDEF extern "C"
+#else
+#define STBIRDEF extern
+#endif
+#endif
+#endif
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Easy-to-use API:
+//
+//     * "input pixels" points to an array of image data with 'num_channels' channels (e.g. RGB=3, RGBA=4)
+//     * input_w is input image width (x-axis), input_h is input image height (y-axis)
+//     * stride is the offset between successive rows of image data in memory, in bytes. you can
+//       specify 0 to mean packed continuously in memory
+//     * alpha channel is treated identically to other channels.
+//     * colorspace is linear or sRGB as specified by function name
+//     * returned result is 1 for success or 0 in case of an error.
+//       #define STBIR_ASSERT() to trigger an assert on parameter validation errors.
+//     * Memory required grows approximately linearly with input and output size, but with
+//       discontinuities at input_w == output_w and input_h == output_h.
+//     * These functions use a "default" resampling filter defined at compile time. To change the filter,
+//       you can change the compile-time defaults by #defining STBIR_DEFAULT_FILTER_UPSAMPLE
+//       and STBIR_DEFAULT_FILTER_DOWNSAMPLE, or you can use the medium-complexity API.
+
+STBIRDEF int stbir_resize_uint8(     const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels);
+
+STBIRDEF int stbir_resize_float(     const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           float *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels);
+
+
+// The following functions interpret image data as gamma-corrected sRGB.
+// Specify STBIR_ALPHA_CHANNEL_NONE if you have no alpha channel,
+// or otherwise provide the index of the alpha channel. Flags value
+// of 0 will probably do the right thing if you're not sure what
+// the flags mean.
+
+#define STBIR_ALPHA_CHANNEL_NONE       -1
+
+// Set this flag if your texture has premultiplied alpha. Otherwise, stbir will
+// use alpha-weighted resampling (effectively premultiplying, resampling,
+// then unpremultiplying).
+#define STBIR_FLAG_ALPHA_PREMULTIPLIED    (1 << 0)
+// The specified alpha channel should be handled as gamma-corrected value even
+// when doing sRGB operations.
+#define STBIR_FLAG_ALPHA_USES_COLORSPACE  (1 << 1)
+
+STBIRDEF int stbir_resize_uint8_srgb(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels, int alpha_channel, int flags);
+
+
+typedef enum
+{
+    STBIR_EDGE_CLAMP   = 1,
+    STBIR_EDGE_REFLECT = 2,
+    STBIR_EDGE_WRAP    = 3,
+    STBIR_EDGE_ZERO    = 4,
+} stbir_edge;
+
+// This function adds the ability to specify how requests to sample off the edge of the image are handled.
+STBIRDEF int stbir_resize_uint8_srgb_edgemode(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                                    unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                              int num_channels, int alpha_channel, int flags,
+                                              stbir_edge edge_wrap_mode);
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Medium-complexity API
+//
+// This extends the easy-to-use API as follows:
+//
+//     * Alpha-channel can be processed separately
+//       * If alpha_channel is not STBIR_ALPHA_CHANNEL_NONE
+//         * Alpha channel will not be gamma corrected (unless flags&STBIR_FLAG_GAMMA_CORRECT)
+//         * Filters will be weighted by alpha channel (unless flags&STBIR_FLAG_ALPHA_PREMULTIPLIED)
+//     * Filter can be selected explicitly
+//     * uint16 image type
+//     * sRGB colorspace available for all types
+//     * context parameter for passing to STBIR_MALLOC
+
+typedef enum
+{
+    STBIR_FILTER_DEFAULT      = 0,  // use same filter type that easy-to-use API chooses
+    STBIR_FILTER_BOX          = 1,  // A trapezoid w/1-pixel wide ramps, same result as box for integer scale ratios
+    STBIR_FILTER_TRIANGLE     = 2,  // On upsampling, produces same results as bilinear texture filtering
+    STBIR_FILTER_CUBICBSPLINE = 3,  // The cubic b-spline (aka Mitchell-Netrevalli with B=1,C=0), gaussian-esque
+    STBIR_FILTER_CATMULLROM   = 4,  // An interpolating cubic spline
+    STBIR_FILTER_MITCHELL     = 5,  // Mitchell-Netrevalli filter with B=1/3, C=1/3
+} stbir_filter;
+
+typedef enum
+{
+    STBIR_COLORSPACE_LINEAR,
+    STBIR_COLORSPACE_SRGB,
+
+    STBIR_MAX_COLORSPACES,
+} stbir_colorspace;
+
+// The following functions are all identical except for the type of the image data
+
+STBIRDEF int stbir_resize_uint8_generic( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                               unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context);
+
+STBIRDEF int stbir_resize_uint16_generic(const stbir_uint16 *input_pixels  , int input_w , int input_h , int input_stride_in_bytes,
+                                               stbir_uint16 *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context);
+
+STBIRDEF int stbir_resize_float_generic( const float *input_pixels         , int input_w , int input_h , int input_stride_in_bytes,
+                                               float *output_pixels        , int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context);
+
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Full-complexity API
+//
+// This extends the medium API as follows:
+//
+//       * uint32 image type
+//     * not typesafe
+//     * separate filter types for each axis
+//     * separate edge modes for each axis
+//     * can specify scale explicitly for subpixel correctness
+//     * can specify image source tile using texture coordinates
+
+typedef enum
+{
+    STBIR_TYPE_UINT8 ,
+    STBIR_TYPE_UINT16,
+    STBIR_TYPE_UINT32,
+    STBIR_TYPE_FLOAT ,
+
+    STBIR_MAX_TYPES
+} stbir_datatype;
+
+STBIRDEF int stbir_resize(         const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context);
+
+STBIRDEF int stbir_resize_subpixel(const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context,
+                                   float x_scale, float y_scale,
+                                   float x_offset, float y_offset);
+
+STBIRDEF int stbir_resize_region(  const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context,
+                                   float s0, float t0, float s1, float t1);
+// (s0, t0) & (s1, t1) are the top-left and bottom right corner (uv addressing style: [0, 1]x[0, 1]) of a region of the input image to use.
+
+//
+//
+////   end header file   /////////////////////////////////////////////////////
+#endif // STBIR_INCLUDE_STB_IMAGE_RESIZE_H
+
+
+
+
+
+#ifdef STB_IMAGE_RESIZE_IMPLEMENTATION
+
+#ifndef STBIR_ASSERT
+#include <assert.h>
+#define STBIR_ASSERT(x) assert(x)
+#endif
+
+// For memset
+#include <string.h>
+
+#include <math.h>
+
+#ifndef STBIR_MALLOC
+#include <stdlib.h>
+// use comma operator to evaluate c, to avoid "unused parameter" warnings
+#define STBIR_MALLOC(size,c) ((void)(c), malloc(size))
+#define STBIR_FREE(ptr,c)    ((void)(c), free(ptr))
+#endif
+
+#ifndef _MSC_VER
+#ifdef __cplusplus
+#define stbir__inline inline
+#else
+#define stbir__inline
+#endif
+#else
+#define stbir__inline __forceinline
+#endif
+
+
+// should produce compiler error if size is wrong
+typedef unsigned char stbir__validate_uint32[sizeof(stbir_uint32) == 4 ? 1 : -1];
+
+#ifdef _MSC_VER
+#define STBIR__NOTUSED(v)  (void)(v)
+#else
+#define STBIR__NOTUSED(v)  (void)sizeof(v)
+#endif
+
+#define STBIR__ARRAY_SIZE(a) (sizeof((a))/sizeof((a)[0]))
+
+#ifndef STBIR_DEFAULT_FILTER_UPSAMPLE
+#define STBIR_DEFAULT_FILTER_UPSAMPLE    STBIR_FILTER_CATMULLROM
+#endif
+
+#ifndef STBIR_DEFAULT_FILTER_DOWNSAMPLE
+#define STBIR_DEFAULT_FILTER_DOWNSAMPLE  STBIR_FILTER_MITCHELL
+#endif
+
+#ifndef STBIR_PROGRESS_REPORT
+#define STBIR_PROGRESS_REPORT(float_0_to_1)
+#endif
+
+#ifndef STBIR_MAX_CHANNELS
+#define STBIR_MAX_CHANNELS 64
+#endif
+
+#if STBIR_MAX_CHANNELS > 65536
+#error "Too many channels; STBIR_MAX_CHANNELS must be no more than 65536."
+// because we store the indices in 16-bit variables
+#endif
+
+// This value is added to alpha just before premultiplication to avoid
+// zeroing out color values. It is equivalent to 2^-80. If you don't want
+// that behavior (it may interfere if you have floating point images with
+// very small alpha values) then you can define STBIR_NO_ALPHA_EPSILON to
+// disable it.
+#ifndef STBIR_ALPHA_EPSILON
+#define STBIR_ALPHA_EPSILON ((float)1 / (1 << 20) / (1 << 20) / (1 << 20) / (1 << 20))
+#endif
+
+
+
+#ifdef _MSC_VER
+#define STBIR__UNUSED_PARAM(v)  (void)(v)
+#else
+#define STBIR__UNUSED_PARAM(v)  (void)sizeof(v)
+#endif
+
+// must match stbir_datatype
+static unsigned char stbir__type_size[] = {
+    1, // STBIR_TYPE_UINT8
+    2, // STBIR_TYPE_UINT16
+    4, // STBIR_TYPE_UINT32
+    4, // STBIR_TYPE_FLOAT
+};
+
+// Kernel function centered at 0
+typedef float (stbir__kernel_fn)(float x, float scale);
+typedef float (stbir__support_fn)(float scale);
+
+typedef struct
+{
+    stbir__kernel_fn* kernel;
+    stbir__support_fn* support;
+} stbir__filter_info;
+
+// When upsampling, the contributors are which source pixels contribute.
+// When downsampling, the contributors are which destination pixels are contributed to.
+typedef struct
+{
+    int n0; // First contributing pixel
+    int n1; // Last contributing pixel
+} stbir__contributors;
+
+typedef struct
+{
+    const void* input_data;
+    int input_w;
+    int input_h;
+    int input_stride_bytes;
+
+    void* output_data;
+    int output_w;
+    int output_h;
+    int output_stride_bytes;
+
+    float s0, t0, s1, t1;
+
+    float horizontal_shift; // Units: output pixels
+    float vertical_shift;   // Units: output pixels
+    float horizontal_scale;
+    float vertical_scale;
+
+    int channels;
+    int alpha_channel;
+    stbir_uint32 flags;
+    stbir_datatype type;
+    stbir_filter horizontal_filter;
+    stbir_filter vertical_filter;
+    stbir_edge edge_horizontal;
+    stbir_edge edge_vertical;
+    stbir_colorspace colorspace;
+
+    stbir__contributors* horizontal_contributors;
+    float* horizontal_coefficients;
+
+    stbir__contributors* vertical_contributors;
+    float* vertical_coefficients;
+
+    int decode_buffer_pixels;
+    float* decode_buffer;
+
+    float* horizontal_buffer;
+
+    // cache these because ceil/floor are inexplicably showing up in profile
+    int horizontal_coefficient_width;
+    int vertical_coefficient_width;
+    int horizontal_filter_pixel_width;
+    int vertical_filter_pixel_width;
+    int horizontal_filter_pixel_margin;
+    int vertical_filter_pixel_margin;
+    int horizontal_num_contributors;
+    int vertical_num_contributors;
+
+    int ring_buffer_length_bytes;   // The length of an individual entry in the ring buffer. The total number of ring buffers is stbir__get_filter_pixel_width(filter)
+    int ring_buffer_num_entries;    // Total number of entries in the ring buffer.
+    int ring_buffer_first_scanline;
+    int ring_buffer_last_scanline;
+    int ring_buffer_begin_index;    // first_scanline is at this index in the ring buffer
+    float* ring_buffer;
+
+    float* encode_buffer; // A temporary buffer to store floats so we don't lose precision while we do multiply-adds.
+
+    int horizontal_contributors_size;
+    int horizontal_coefficients_size;
+    int vertical_contributors_size;
+    int vertical_coefficients_size;
+    int decode_buffer_size;
+    int horizontal_buffer_size;
+    int ring_buffer_size;
+    int encode_buffer_size;
+} stbir__info;
+
+
+static const float stbir__max_uint8_as_float  = 255.0f;
+static const float stbir__max_uint16_as_float = 65535.0f;
+static const double stbir__max_uint32_as_float = 4294967295.0;
+
+
+static stbir__inline int stbir__min(int a, int b)
+{
+    return a < b ? a : b;
+}
+
+static stbir__inline float stbir__saturate(float x)
+{
+    if (x < 0)
+        return 0;
+
+    if (x > 1)
+        return 1;
+
+    return x;
+}
+
+#ifdef STBIR_SATURATE_INT
+static stbir__inline stbir_uint8 stbir__saturate8(int x)
+{
+    if ((unsigned int) x <= 255)
+        return x;
+
+    if (x < 0)
+        return 0;
+
+    return 255;
+}
+
+static stbir__inline stbir_uint16 stbir__saturate16(int x)
+{
+    if ((unsigned int) x <= 65535)
+        return x;
+
+    if (x < 0)
+        return 0;
+
+    return 65535;
+}
+#endif
+
+static float stbir__srgb_uchar_to_linear_float[256] = {
+    0.000000f, 0.000304f, 0.000607f, 0.000911f, 0.001214f, 0.001518f, 0.001821f, 0.002125f, 0.002428f, 0.002732f, 0.003035f,
+    0.003347f, 0.003677f, 0.004025f, 0.004391f, 0.004777f, 0.005182f, 0.005605f, 0.006049f, 0.006512f, 0.006995f, 0.007499f,
+    0.008023f, 0.008568f, 0.009134f, 0.009721f, 0.010330f, 0.010960f, 0.011612f, 0.012286f, 0.012983f, 0.013702f, 0.014444f,
+    0.015209f, 0.015996f, 0.016807f, 0.017642f, 0.018500f, 0.019382f, 0.020289f, 0.021219f, 0.022174f, 0.023153f, 0.024158f,
+    0.025187f, 0.026241f, 0.027321f, 0.028426f, 0.029557f, 0.030713f, 0.031896f, 0.033105f, 0.034340f, 0.035601f, 0.036889f,
+    0.038204f, 0.039546f, 0.040915f, 0.042311f, 0.043735f, 0.045186f, 0.046665f, 0.048172f, 0.049707f, 0.051269f, 0.052861f,
+    0.054480f, 0.056128f, 0.057805f, 0.059511f, 0.061246f, 0.063010f, 0.064803f, 0.066626f, 0.068478f, 0.070360f, 0.072272f,
+    0.074214f, 0.076185f, 0.078187f, 0.080220f, 0.082283f, 0.084376f, 0.086500f, 0.088656f, 0.090842f, 0.093059f, 0.095307f,
+    0.097587f, 0.099899f, 0.102242f, 0.104616f, 0.107023f, 0.109462f, 0.111932f, 0.114435f, 0.116971f, 0.119538f, 0.122139f,
+    0.124772f, 0.127438f, 0.130136f, 0.132868f, 0.135633f, 0.138432f, 0.141263f, 0.144128f, 0.147027f, 0.149960f, 0.152926f,
+    0.155926f, 0.158961f, 0.162029f, 0.165132f, 0.168269f, 0.171441f, 0.174647f, 0.177888f, 0.181164f, 0.184475f, 0.187821f,
+    0.191202f, 0.194618f, 0.198069f, 0.201556f, 0.205079f, 0.208637f, 0.212231f, 0.215861f, 0.219526f, 0.223228f, 0.226966f,
+    0.230740f, 0.234551f, 0.238398f, 0.242281f, 0.246201f, 0.250158f, 0.254152f, 0.258183f, 0.262251f, 0.266356f, 0.270498f,
+    0.274677f, 0.278894f, 0.283149f, 0.287441f, 0.291771f, 0.296138f, 0.300544f, 0.304987f, 0.309469f, 0.313989f, 0.318547f,
+    0.323143f, 0.327778f, 0.332452f, 0.337164f, 0.341914f, 0.346704f, 0.351533f, 0.356400f, 0.361307f, 0.366253f, 0.371238f,
+    0.376262f, 0.381326f, 0.386430f, 0.391573f, 0.396755f, 0.401978f, 0.407240f, 0.412543f, 0.417885f, 0.423268f, 0.428691f,
+    0.434154f, 0.439657f, 0.445201f, 0.450786f, 0.456411f, 0.462077f, 0.467784f, 0.473532f, 0.479320f, 0.485150f, 0.491021f,
+    0.496933f, 0.502887f, 0.508881f, 0.514918f, 0.520996f, 0.527115f, 0.533276f, 0.539480f, 0.545725f, 0.552011f, 0.558340f,
+    0.564712f, 0.571125f, 0.577581f, 0.584078f, 0.590619f, 0.597202f, 0.603827f, 0.610496f, 0.617207f, 0.623960f, 0.630757f,
+    0.637597f, 0.644480f, 0.651406f, 0.658375f, 0.665387f, 0.672443f, 0.679543f, 0.686685f, 0.693872f, 0.701102f, 0.708376f,
+    0.715694f, 0.723055f, 0.730461f, 0.737911f, 0.745404f, 0.752942f, 0.760525f, 0.768151f, 0.775822f, 0.783538f, 0.791298f,
+    0.799103f, 0.806952f, 0.814847f, 0.822786f, 0.830770f, 0.838799f, 0.846873f, 0.854993f, 0.863157f, 0.871367f, 0.879622f,
+    0.887923f, 0.896269f, 0.904661f, 0.913099f, 0.921582f, 0.930111f, 0.938686f, 0.947307f, 0.955974f, 0.964686f, 0.973445f,
+    0.982251f, 0.991102f, 1.0f
+};
+
+static float stbir__srgb_to_linear(float f)
+{
+    if (f <= 0.04045f)
+        return f / 12.92f;
+    else
+        return (float)pow((f + 0.055f) / 1.055f, 2.4f);
+}
+
+static float stbir__linear_to_srgb(float f)
+{
+    if (f <= 0.0031308f)
+        return f * 12.92f;
+    else
+        return 1.055f * (float)pow(f, 1 / 2.4f) - 0.055f;
+}
+
+#ifndef STBIR_NON_IEEE_FLOAT
+// From https://gist.github.com/rygorous/2203834
+
+typedef union
+{
+    stbir_uint32 u;
+    float f;
+} stbir__FP32;
+
+static const stbir_uint32 fp32_to_srgb8_tab4[104] = {
+    0x0073000d, 0x007a000d, 0x0080000d, 0x0087000d, 0x008d000d, 0x0094000d, 0x009a000d, 0x00a1000d,
+    0x00a7001a, 0x00b4001a, 0x00c1001a, 0x00ce001a, 0x00da001a, 0x00e7001a, 0x00f4001a, 0x0101001a,
+    0x010e0033, 0x01280033, 0x01410033, 0x015b0033, 0x01750033, 0x018f0033, 0x01a80033, 0x01c20033,
+    0x01dc0067, 0x020f0067, 0x02430067, 0x02760067, 0x02aa0067, 0x02dd0067, 0x03110067, 0x03440067,
+    0x037800ce, 0x03df00ce, 0x044600ce, 0x04ad00ce, 0x051400ce, 0x057b00c5, 0x05dd00bc, 0x063b00b5,
+    0x06970158, 0x07420142, 0x07e30130, 0x087b0120, 0x090b0112, 0x09940106, 0x0a1700fc, 0x0a9500f2,
+    0x0b0f01cb, 0x0bf401ae, 0x0ccb0195, 0x0d950180, 0x0e56016e, 0x0f0d015e, 0x0fbc0150, 0x10630143,
+    0x11070264, 0x1238023e, 0x1357021d, 0x14660201, 0x156601e9, 0x165a01d3, 0x174401c0, 0x182401af,
+    0x18fe0331, 0x1a9602fe, 0x1c1502d2, 0x1d7e02ad, 0x1ed4028d, 0x201a0270, 0x21520256, 0x227d0240,
+    0x239f0443, 0x25c003fe, 0x27bf03c4, 0x29a10392, 0x2b6a0367, 0x2d1d0341, 0x2ebe031f, 0x304d0300,
+    0x31d105b0, 0x34a80555, 0x37520507, 0x39d504c5, 0x3c37048b, 0x3e7c0458, 0x40a8042a, 0x42bd0401,
+    0x44c20798, 0x488e071e, 0x4c1c06b6, 0x4f76065d, 0x52a50610, 0x55ac05cc, 0x5892058f, 0x5b590559,
+    0x5e0c0a23, 0x631c0980, 0x67db08f6, 0x6c55087f, 0x70940818, 0x74a007bd, 0x787d076c, 0x7c330723,
+};
+
+static stbir_uint8 stbir__linear_to_srgb_uchar(float in)
+{
+    static const stbir__FP32 almostone = { 0x3f7fffff }; // 1-eps
+    static const stbir__FP32 minval = { (127-13) << 23 };
+    stbir_uint32 tab,bias,scale,t;
+    stbir__FP32 f;
+
+    // Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
+    // The tests are carefully written so that NaNs map to 0, same as in the reference
+    // implementation.
+    if (!(in > minval.f)) // written this way to catch NaNs
+        in = minval.f;
+    if (in > almostone.f)
+        in = almostone.f;
+
+    // Do the table lookup and unpack bias, scale
+    f.f = in;
+    tab = fp32_to_srgb8_tab4[(f.u - minval.u) >> 20];
+    bias = (tab >> 16) << 9;
+    scale = tab & 0xffff;
+
+    // Grab next-highest mantissa bits and perform linear interpolation
+    t = (f.u >> 12) & 0xff;
+    return (unsigned char) ((bias + scale*t) >> 16);
+}
+
+#else
+// sRGB transition values, scaled by 1<<28
+static int stbir__srgb_offset_to_linear_scaled[256] =
+{
+            0,     40738,    122216,    203693,    285170,    366648,    448125,    529603,
+       611080,    692557,    774035,    855852,    942009,   1033024,   1128971,   1229926,
+      1335959,   1447142,   1563542,   1685229,   1812268,   1944725,   2082664,   2226148,
+      2375238,   2529996,   2690481,   2856753,   3028870,   3206888,   3390865,   3580856,
+      3776916,   3979100,   4187460,   4402049,   4622919,   4850123,   5083710,   5323731,
+      5570236,   5823273,   6082892,   6349140,   6622065,   6901714,   7188133,   7481369,
+      7781466,   8088471,   8402427,   8723380,   9051372,   9386448,   9728650,  10078021,
+     10434603,  10798439,  11169569,  11548036,  11933879,  12327139,  12727857,  13136073,
+     13551826,  13975156,  14406100,  14844697,  15290987,  15745007,  16206795,  16676389,
+     17153826,  17639142,  18132374,  18633560,  19142734,  19659934,  20185196,  20718552,
+     21260042,  21809696,  22367554,  22933648,  23508010,  24090680,  24681686,  25281066,
+     25888850,  26505076,  27129772,  27762974,  28404716,  29055026,  29713942,  30381490,
+     31057708,  31742624,  32436272,  33138682,  33849884,  34569912,  35298800,  36036568,
+     36783260,  37538896,  38303512,  39077136,  39859796,  40651528,  41452360,  42262316,
+     43081432,  43909732,  44747252,  45594016,  46450052,  47315392,  48190064,  49074096,
+     49967516,  50870356,  51782636,  52704392,  53635648,  54576432,  55526772,  56486700,
+     57456236,  58435408,  59424248,  60422780,  61431036,  62449032,  63476804,  64514376,
+     65561776,  66619028,  67686160,  68763192,  69850160,  70947088,  72053992,  73170912,
+     74297864,  75434880,  76581976,  77739184,  78906536,  80084040,  81271736,  82469648,
+     83677792,  84896192,  86124888,  87363888,  88613232,  89872928,  91143016,  92423512,
+     93714432,  95015816,  96327688,  97650056,  98982952, 100326408, 101680440, 103045072,
+    104420320, 105806224, 107202800, 108610064, 110028048, 111456776, 112896264, 114346544,
+    115807632, 117279552, 118762328, 120255976, 121760536, 123276016, 124802440, 126339832,
+    127888216, 129447616, 131018048, 132599544, 134192112, 135795792, 137410592, 139036528,
+    140673648, 142321952, 143981456, 145652208, 147334208, 149027488, 150732064, 152447968,
+    154175200, 155913792, 157663776, 159425168, 161197984, 162982240, 164777968, 166585184,
+    168403904, 170234160, 172075968, 173929344, 175794320, 177670896, 179559120, 181458992,
+    183370528, 185293776, 187228736, 189175424, 191133888, 193104112, 195086128, 197079968,
+    199085648, 201103184, 203132592, 205173888, 207227120, 209292272, 211369392, 213458480,
+    215559568, 217672656, 219797792, 221934976, 224084240, 226245600, 228419056, 230604656,
+    232802400, 235012320, 237234432, 239468736, 241715280, 243974080, 246245120, 248528464,
+    250824112, 253132064, 255452368, 257785040, 260130080, 262487520, 264857376, 267239664,
+};
+
+static stbir_uint8 stbir__linear_to_srgb_uchar(float f)
+{
+    int x = (int) (f * (1 << 28)); // has headroom so you don't need to clamp
+    int v = 0;
+    int i;
+
+    // Refine the guess with a short binary search.
+    i = v + 128; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +  64; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +  32; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +  16; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +   8; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +   4; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +   2; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+    i = v +   1; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
+
+    return (stbir_uint8) v;
+}
+#endif
+
+static float stbir__filter_trapezoid(float x, float scale)
+{
+    float halfscale = scale / 2;
+    float t = 0.5f + halfscale;
+    STBIR_ASSERT(scale <= 1);
+
+    x = (float)fabs(x);
+
+    if (x >= t)
+        return 0;
+    else
+    {
+        float r = 0.5f - halfscale;
+        if (x <= r)
+            return 1;
+        else
+            return (t - x) / scale;
+    }
+}
+
+static float stbir__support_trapezoid(float scale)
+{
+    STBIR_ASSERT(scale <= 1);
+    return 0.5f + scale / 2;
+}
+
+static float stbir__filter_triangle(float x, float s)
+{
+    STBIR__UNUSED_PARAM(s);
+
+    x = (float)fabs(x);
+
+    if (x <= 1.0f)
+        return 1 - x;
+    else
+        return 0;
+}
+
+static float stbir__filter_cubic(float x, float s)
+{
+    STBIR__UNUSED_PARAM(s);
+
+    x = (float)fabs(x);
+
+    if (x < 1.0f)
+        return (4 + x*x*(3*x - 6))/6;
+    else if (x < 2.0f)
+        return (8 + x*(-12 + x*(6 - x)))/6;
+
+    return (0.0f);
+}
+
+static float stbir__filter_catmullrom(float x, float s)
+{
+    STBIR__UNUSED_PARAM(s);
+
+    x = (float)fabs(x);
+
+    if (x < 1.0f)
+        return 1 - x*x*(2.5f - 1.5f*x);
+    else if (x < 2.0f)
+        return 2 - x*(4 + x*(0.5f*x - 2.5f));
+
+    return (0.0f);
+}
+
+static float stbir__filter_mitchell(float x, float s)
+{
+    STBIR__UNUSED_PARAM(s);
+
+    x = (float)fabs(x);
+
+    if (x < 1.0f)
+        return (16 + x*x*(21 * x - 36))/18;
+    else if (x < 2.0f)
+        return (32 + x*(-60 + x*(36 - 7*x)))/18;
+
+    return (0.0f);
+}
+
+static float stbir__support_zero(float s)
+{
+    STBIR__UNUSED_PARAM(s);
+    return 0;
+}
+
+static float stbir__support_one(float s)
+{
+    STBIR__UNUSED_PARAM(s);
+    return 1;
+}
+
+static float stbir__support_two(float s)
+{
+    STBIR__UNUSED_PARAM(s);
+    return 2;
+}
+
+static stbir__filter_info stbir__filter_info_table[] = {
+        { NULL,                     stbir__support_zero },
+        { stbir__filter_trapezoid,  stbir__support_trapezoid },
+        { stbir__filter_triangle,   stbir__support_one },
+        { stbir__filter_cubic,      stbir__support_two },
+        { stbir__filter_catmullrom, stbir__support_two },
+        { stbir__filter_mitchell,   stbir__support_two },
+};
+
+stbir__inline static int stbir__use_upsampling(float ratio)
+{
+    return ratio > 1;
+}
+
+stbir__inline static int stbir__use_width_upsampling(stbir__info* stbir_info)
+{
+    return stbir__use_upsampling(stbir_info->horizontal_scale);
+}
+
+stbir__inline static int stbir__use_height_upsampling(stbir__info* stbir_info)
+{
+    return stbir__use_upsampling(stbir_info->vertical_scale);
+}
+
+// This is the maximum number of input samples that can affect an output sample
+// with the given filter
+static int stbir__get_filter_pixel_width(stbir_filter filter, float scale)
+{
+    STBIR_ASSERT(filter != 0);
+    STBIR_ASSERT(filter < STBIR__ARRAY_SIZE(stbir__filter_info_table));
+
+    if (stbir__use_upsampling(scale))
+        return (int)ceil(stbir__filter_info_table[filter].support(1/scale) * 2);
+    else
+        return (int)ceil(stbir__filter_info_table[filter].support(scale) * 2 / scale);
+}
+
+// This is how much to expand buffers to account for filters seeking outside
+// the image boundaries.
+static int stbir__get_filter_pixel_margin(stbir_filter filter, float scale)
+{
+    return stbir__get_filter_pixel_width(filter, scale) / 2;
+}
+
+static int stbir__get_coefficient_width(stbir_filter filter, float scale)
+{
+    if (stbir__use_upsampling(scale))
+        return (int)ceil(stbir__filter_info_table[filter].support(1 / scale) * 2);
+    else
+        return (int)ceil(stbir__filter_info_table[filter].support(scale) * 2);
+}
+
+static int stbir__get_contributors(float scale, stbir_filter filter, int input_size, int output_size)
+{
+    if (stbir__use_upsampling(scale))
+        return output_size;
+    else
+        return (input_size + stbir__get_filter_pixel_margin(filter, scale) * 2);
+}
+
+static int stbir__get_total_horizontal_coefficients(stbir__info* info)
+{
+    return info->horizontal_num_contributors
+         * stbir__get_coefficient_width      (info->horizontal_filter, info->horizontal_scale);
+}
+
+static int stbir__get_total_vertical_coefficients(stbir__info* info)
+{
+    return info->vertical_num_contributors
+         * stbir__get_coefficient_width      (info->vertical_filter, info->vertical_scale);
+}
+
+static stbir__contributors* stbir__get_contributor(stbir__contributors* contributors, int n)
+{
+    return &contributors[n];
+}
+
+// For perf reasons this code is duplicated in stbir__resample_horizontal_upsample/downsample,
+// if you change it here change it there too.
+static float* stbir__get_coefficient(float* coefficients, stbir_filter filter, float scale, int n, int c)
+{
+    int width = stbir__get_coefficient_width(filter, scale);
+    return &coefficients[width*n + c];
+}
+
+static int stbir__edge_wrap_slow(stbir_edge edge, int n, int max)
+{
+    switch (edge)
+    {
+    case STBIR_EDGE_ZERO:
+        return 0; // we'll decode the wrong pixel here, and then overwrite with 0s later
+
+    case STBIR_EDGE_CLAMP:
+        if (n < 0)
+            return 0;
+
+        if (n >= max)
+            return max - 1;
+
+        return n; // NOTREACHED
+
+    case STBIR_EDGE_REFLECT:
+    {
+        if (n < 0)
+        {
+            if (n < max)
+                return -n;
+            else
+                return max - 1;
+        }
+
+        if (n >= max)
+        {
+            int max2 = max * 2;
+            if (n >= max2)
+                return 0;
+            else
+                return max2 - n - 1;
+        }
+
+        return n; // NOTREACHED
+    }
+
+    case STBIR_EDGE_WRAP:
+        if (n >= 0)
+            return (n % max);
+        else
+        {
+            int m = (-n) % max;
+
+            if (m != 0)
+                m = max - m;
+
+            return (m);
+        }
+        // NOTREACHED
+
+    default:
+        STBIR_ASSERT(!"Unimplemented edge type");
+        return 0;
+    }
+}
+
+stbir__inline static int stbir__edge_wrap(stbir_edge edge, int n, int max)
+{
+    // avoid per-pixel switch
+    if (n >= 0 && n < max)
+        return n;
+    return stbir__edge_wrap_slow(edge, n, max);
+}
+
+// What input pixels contribute to this output pixel?
+static void stbir__calculate_sample_range_upsample(int n, float out_filter_radius, float scale_ratio, float out_shift, int* in_first_pixel, int* in_last_pixel, float* in_center_of_out)
+{
+    float out_pixel_center = (float)n + 0.5f;
+    float out_pixel_influence_lowerbound = out_pixel_center - out_filter_radius;
+    float out_pixel_influence_upperbound = out_pixel_center + out_filter_radius;
+
+    float in_pixel_influence_lowerbound = (out_pixel_influence_lowerbound + out_shift) / scale_ratio;
+    float in_pixel_influence_upperbound = (out_pixel_influence_upperbound + out_shift) / scale_ratio;
+
+    *in_center_of_out = (out_pixel_center + out_shift) / scale_ratio;
+    *in_first_pixel = (int)(floor(in_pixel_influence_lowerbound + 0.5));
+    *in_last_pixel = (int)(floor(in_pixel_influence_upperbound - 0.5));
+}
+
+// What output pixels does this input pixel contribute to?
+static void stbir__calculate_sample_range_downsample(int n, float in_pixels_radius, float scale_ratio, float out_shift, int* out_first_pixel, int* out_last_pixel, float* out_center_of_in)
+{
+    float in_pixel_center = (float)n + 0.5f;
+    float in_pixel_influence_lowerbound = in_pixel_center - in_pixels_radius;
+    float in_pixel_influence_upperbound = in_pixel_center + in_pixels_radius;
+
+    float out_pixel_influence_lowerbound = in_pixel_influence_lowerbound * scale_ratio - out_shift;
+    float out_pixel_influence_upperbound = in_pixel_influence_upperbound * scale_ratio - out_shift;
+
+    *out_center_of_in = in_pixel_center * scale_ratio - out_shift;
+    *out_first_pixel = (int)(floor(out_pixel_influence_lowerbound + 0.5));
+    *out_last_pixel = (int)(floor(out_pixel_influence_upperbound - 0.5));
+}
+
+static void stbir__calculate_coefficients_upsample(stbir_filter filter, float scale, int in_first_pixel, int in_last_pixel, float in_center_of_out, stbir__contributors* contributor, float* coefficient_group)
+{
+    int i;
+    float total_filter = 0;
+    float filter_scale;
+
+    STBIR_ASSERT(in_last_pixel - in_first_pixel <= (int)ceil(stbir__filter_info_table[filter].support(1/scale) * 2)); // Taken directly from stbir__get_coefficient_width() which we can't call because we don't know if we're horizontal or vertical.
+
+    contributor->n0 = in_first_pixel;
+    contributor->n1 = in_last_pixel;
+
+    STBIR_ASSERT(contributor->n1 >= contributor->n0);
+
+    for (i = 0; i <= in_last_pixel - in_first_pixel; i++)
+    {
+        float in_pixel_center = (float)(i + in_first_pixel) + 0.5f;
+        coefficient_group[i] = stbir__filter_info_table[filter].kernel(in_center_of_out - in_pixel_center, 1 / scale);
+
+        // If the coefficient is zero, skip it. (Don't do the <0 check here, we want the influence of those outside pixels.)
+        if (i == 0 && !coefficient_group[i])
+        {
+            contributor->n0 = ++in_first_pixel;
+            i--;
+            continue;
+        }
+
+        total_filter += coefficient_group[i];
+    }
+
+    STBIR_ASSERT(stbir__filter_info_table[filter].kernel((float)(in_last_pixel + 1) + 0.5f - in_center_of_out, 1/scale) == 0);
+
+    STBIR_ASSERT(total_filter > 0.9);
+    STBIR_ASSERT(total_filter < 1.1f); // Make sure it's not way off.
+
+    // Make sure the sum of all coefficients is 1.
+    filter_scale = 1 / total_filter;
+
+    for (i = 0; i <= in_last_pixel - in_first_pixel; i++)
+        coefficient_group[i] *= filter_scale;
+
+    for (i = in_last_pixel - in_first_pixel; i >= 0; i--)
+    {
+        if (coefficient_group[i])
+            break;
+
+        // This line has no weight. We can skip it.
+        contributor->n1 = contributor->n0 + i - 1;
+    }
+}
+
+static void stbir__calculate_coefficients_downsample(stbir_filter filter, float scale_ratio, int out_first_pixel, int out_last_pixel, float out_center_of_in, stbir__contributors* contributor, float* coefficient_group)
+{
+    int i;
+
+     STBIR_ASSERT(out_last_pixel - out_first_pixel <= (int)ceil(stbir__filter_info_table[filter].support(scale_ratio) * 2)); // Taken directly from stbir__get_coefficient_width() which we can't call because we don't know if we're horizontal or vertical.
+
+    contributor->n0 = out_first_pixel;
+    contributor->n1 = out_last_pixel;
+
+    STBIR_ASSERT(contributor->n1 >= contributor->n0);
+
+    for (i = 0; i <= out_last_pixel - out_first_pixel; i++)
+    {
+        float out_pixel_center = (float)(i + out_first_pixel) + 0.5f;
+        float x = out_pixel_center - out_center_of_in;
+        coefficient_group[i] = stbir__filter_info_table[filter].kernel(x, scale_ratio) * scale_ratio;
+    }
+
+    STBIR_ASSERT(stbir__filter_info_table[filter].kernel((float)(out_last_pixel + 1) + 0.5f - out_center_of_in, scale_ratio) == 0);
+
+    for (i = out_last_pixel - out_first_pixel; i >= 0; i--)
+    {
+        if (coefficient_group[i])
+            break;
+
+        // This line has no weight. We can skip it.
+        contributor->n1 = contributor->n0 + i - 1;
+    }
+}
+
+static void stbir__normalize_downsample_coefficients(stbir__contributors* contributors, float* coefficients, stbir_filter filter, float scale_ratio, int input_size, int output_size)
+{
+    int num_contributors = stbir__get_contributors(scale_ratio, filter, input_size, output_size);
+    int num_coefficients = stbir__get_coefficient_width(filter, scale_ratio);
+    int i, j;
+    int skip;
+
+    for (i = 0; i < output_size; i++)
+    {
+        float scale;
+        float total = 0;
+
+        for (j = 0; j < num_contributors; j++)
+        {
+            if (i >= contributors[j].n0 && i <= contributors[j].n1)
+            {
+                float coefficient = *stbir__get_coefficient(coefficients, filter, scale_ratio, j, i - contributors[j].n0);
+                total += coefficient;
+            }
+            else if (i < contributors[j].n0)
+                break;
+        }
+
+        STBIR_ASSERT(total > 0.9f);
+        STBIR_ASSERT(total < 1.1f);
+
+        scale = 1 / total;
+
+        for (j = 0; j < num_contributors; j++)
+        {
+            if (i >= contributors[j].n0 && i <= contributors[j].n1)
+                *stbir__get_coefficient(coefficients, filter, scale_ratio, j, i - contributors[j].n0) *= scale;
+            else if (i < contributors[j].n0)
+                break;
+        }
+    }
+
+    // Optimize: Skip zero coefficients and contributions outside of image bounds.
+    // Do this after normalizing because normalization depends on the n0/n1 values.
+    for (j = 0; j < num_contributors; j++)
+    {
+        int range, max, width;
+
+        skip = 0;
+        while (*stbir__get_coefficient(coefficients, filter, scale_ratio, j, skip) == 0)
+            skip++;
+
+        contributors[j].n0 += skip;
+
+        while (contributors[j].n0 < 0)
+        {
+            contributors[j].n0++;
+            skip++;
+        }
+
+        range = contributors[j].n1 - contributors[j].n0 + 1;
+        max = stbir__min(num_coefficients, range);
+
+        width = stbir__get_coefficient_width(filter, scale_ratio);
+        for (i = 0; i < max; i++)
+        {
+            if (i + skip >= width)
+                break;
+
+            *stbir__get_coefficient(coefficients, filter, scale_ratio, j, i) = *stbir__get_coefficient(coefficients, filter, scale_ratio, j, i + skip);
+        }
+
+        continue;
+    }
+
+    // Using min to avoid writing into invalid pixels.
+    for (i = 0; i < num_contributors; i++)
+        contributors[i].n1 = stbir__min(contributors[i].n1, output_size - 1);
+}
+
+// Each scan line uses the same kernel values so we should calculate the kernel
+// values once and then we can use them for every scan line.
+static void stbir__calculate_filters(stbir__contributors* contributors, float* coefficients, stbir_filter filter, float scale_ratio, float shift, int input_size, int output_size)
+{
+    int n;
+    int total_contributors = stbir__get_contributors(scale_ratio, filter, input_size, output_size);
+
+    if (stbir__use_upsampling(scale_ratio))
+    {
+        float out_pixels_radius = stbir__filter_info_table[filter].support(1 / scale_ratio) * scale_ratio;
+
+        // Looping through out pixels
+        for (n = 0; n < total_contributors; n++)
+        {
+            float in_center_of_out; // Center of the current out pixel in the in pixel space
+            int in_first_pixel, in_last_pixel;
+
+            stbir__calculate_sample_range_upsample(n, out_pixels_radius, scale_ratio, shift, &in_first_pixel, &in_last_pixel, &in_center_of_out);
+
+            stbir__calculate_coefficients_upsample(filter, scale_ratio, in_first_pixel, in_last_pixel, in_center_of_out, stbir__get_contributor(contributors, n), stbir__get_coefficient(coefficients, filter, scale_ratio, n, 0));
+        }
+    }
+    else
+    {
+        float in_pixels_radius = stbir__filter_info_table[filter].support(scale_ratio) / scale_ratio;
+
+        // Looping through in pixels
+        for (n = 0; n < total_contributors; n++)
+        {
+            float out_center_of_in; // Center of the current out pixel in the in pixel space
+            int out_first_pixel, out_last_pixel;
+            int n_adjusted = n - stbir__get_filter_pixel_margin(filter, scale_ratio);
+
+            stbir__calculate_sample_range_downsample(n_adjusted, in_pixels_radius, scale_ratio, shift, &out_first_pixel, &out_last_pixel, &out_center_of_in);
+
+            stbir__calculate_coefficients_downsample(filter, scale_ratio, out_first_pixel, out_last_pixel, out_center_of_in, stbir__get_contributor(contributors, n), stbir__get_coefficient(coefficients, filter, scale_ratio, n, 0));
+        }
+
+        stbir__normalize_downsample_coefficients(contributors, coefficients, filter, scale_ratio, input_size, output_size);
+    }
+}
+
+static float* stbir__get_decode_buffer(stbir__info* stbir_info)
+{
+    // The 0 index of the decode buffer starts after the margin. This makes
+    // it okay to use negative indexes on the decode buffer.
+    return &stbir_info->decode_buffer[stbir_info->horizontal_filter_pixel_margin * stbir_info->channels];
+}
+
+#define STBIR__DECODE(type, colorspace) ((int)(type) * (STBIR_MAX_COLORSPACES) + (int)(colorspace))
+
+static void stbir__decode_scanline(stbir__info* stbir_info, int n)
+{
+    int c;
+    int channels = stbir_info->channels;
+    int alpha_channel = stbir_info->alpha_channel;
+    int type = stbir_info->type;
+    int colorspace = stbir_info->colorspace;
+    int input_w = stbir_info->input_w;
+    size_t input_stride_bytes = stbir_info->input_stride_bytes;
+    float* decode_buffer = stbir__get_decode_buffer(stbir_info);
+    stbir_edge edge_horizontal = stbir_info->edge_horizontal;
+    stbir_edge edge_vertical = stbir_info->edge_vertical;
+    size_t in_buffer_row_offset = stbir__edge_wrap(edge_vertical, n, stbir_info->input_h) * input_stride_bytes;
+    const void* input_data = (char *) stbir_info->input_data + in_buffer_row_offset;
+    int max_x = input_w + stbir_info->horizontal_filter_pixel_margin;
+    int decode = STBIR__DECODE(type, colorspace);
+
+    int x = -stbir_info->horizontal_filter_pixel_margin;
+
+    // special handling for STBIR_EDGE_ZERO because it needs to return an item that doesn't appear in the input,
+    // and we want to avoid paying overhead on every pixel if not STBIR_EDGE_ZERO
+    if (edge_vertical == STBIR_EDGE_ZERO && (n < 0 || n >= stbir_info->input_h))
+    {
+        for (; x < max_x; x++)
+            for (c = 0; c < channels; c++)
+                decode_buffer[x*channels + c] = 0;
+        return;
+    }
+
+    switch (decode)
+    {
+    case STBIR__DECODE(STBIR_TYPE_UINT8, STBIR_COLORSPACE_LINEAR):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = ((float)((const unsigned char*)input_data)[input_pixel_index + c]) / stbir__max_uint8_as_float;
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_UINT8, STBIR_COLORSPACE_SRGB):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = stbir__srgb_uchar_to_linear_float[((const unsigned char*)input_data)[input_pixel_index + c]];
+
+            if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                decode_buffer[decode_pixel_index + alpha_channel] = ((float)((const unsigned char*)input_data)[input_pixel_index + alpha_channel]) / stbir__max_uint8_as_float;
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_UINT16, STBIR_COLORSPACE_LINEAR):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = ((float)((const unsigned short*)input_data)[input_pixel_index + c]) / stbir__max_uint16_as_float;
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_UINT16, STBIR_COLORSPACE_SRGB):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = stbir__srgb_to_linear(((float)((const unsigned short*)input_data)[input_pixel_index + c]) / stbir__max_uint16_as_float);
+
+            if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                decode_buffer[decode_pixel_index + alpha_channel] = ((float)((const unsigned short*)input_data)[input_pixel_index + alpha_channel]) / stbir__max_uint16_as_float;
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_UINT32, STBIR_COLORSPACE_LINEAR):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = (float)(((double)((const unsigned int*)input_data)[input_pixel_index + c]) / stbir__max_uint32_as_float);
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_UINT32, STBIR_COLORSPACE_SRGB):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = stbir__srgb_to_linear((float)(((double)((const unsigned int*)input_data)[input_pixel_index + c]) / stbir__max_uint32_as_float));
+
+            if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                decode_buffer[decode_pixel_index + alpha_channel] = (float)(((double)((const unsigned int*)input_data)[input_pixel_index + alpha_channel]) / stbir__max_uint32_as_float);
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_FLOAT, STBIR_COLORSPACE_LINEAR):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = ((const float*)input_data)[input_pixel_index + c];
+        }
+        break;
+
+    case STBIR__DECODE(STBIR_TYPE_FLOAT, STBIR_COLORSPACE_SRGB):
+        for (; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+            int input_pixel_index = stbir__edge_wrap(edge_horizontal, x, input_w) * channels;
+            for (c = 0; c < channels; c++)
+                decode_buffer[decode_pixel_index + c] = stbir__srgb_to_linear(((const float*)input_data)[input_pixel_index + c]);
+
+            if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                decode_buffer[decode_pixel_index + alpha_channel] = ((const float*)input_data)[input_pixel_index + alpha_channel];
+        }
+
+        break;
+
+    default:
+        STBIR_ASSERT(!"Unknown type/colorspace/channels combination.");
+        break;
+    }
+
+    if (!(stbir_info->flags & STBIR_FLAG_ALPHA_PREMULTIPLIED))
+    {
+        for (x = -stbir_info->horizontal_filter_pixel_margin; x < max_x; x++)
+        {
+            int decode_pixel_index = x * channels;
+
+            // If the alpha value is 0 it will clobber the color values. Make sure it's not.
+            float alpha = decode_buffer[decode_pixel_index + alpha_channel];
+#ifndef STBIR_NO_ALPHA_EPSILON
+            if (stbir_info->type != STBIR_TYPE_FLOAT) {
+                alpha += STBIR_ALPHA_EPSILON;
+                decode_buffer[decode_pixel_index + alpha_channel] = alpha;
+            }
+#endif
+            for (c = 0; c < channels; c++)
+            {
+                if (c == alpha_channel)
+                    continue;
+
+                decode_buffer[decode_pixel_index + c] *= alpha;
+            }
+        }
+    }
+
+    if (edge_horizontal == STBIR_EDGE_ZERO)
+    {
+        for (x = -stbir_info->horizontal_filter_pixel_margin; x < 0; x++)
+        {
+            for (c = 0; c < channels; c++)
+                decode_buffer[x*channels + c] = 0;
+        }
+        for (x = input_w; x < max_x; x++)
+        {
+            for (c = 0; c < channels; c++)
+                decode_buffer[x*channels + c] = 0;
+        }
+    }
+}
+
+static float* stbir__get_ring_buffer_entry(float* ring_buffer, int index, int ring_buffer_length)
+{
+    return &ring_buffer[index * ring_buffer_length];
+}
+
+static float* stbir__add_empty_ring_buffer_entry(stbir__info* stbir_info, int n)
+{
+    int ring_buffer_index;
+    float* ring_buffer;
+
+    stbir_info->ring_buffer_last_scanline = n;
+
+    if (stbir_info->ring_buffer_begin_index < 0)
+    {
+        ring_buffer_index = stbir_info->ring_buffer_begin_index = 0;
+        stbir_info->ring_buffer_first_scanline = n;
+    }
+    else
+    {
+        ring_buffer_index = (stbir_info->ring_buffer_begin_index + (stbir_info->ring_buffer_last_scanline - stbir_info->ring_buffer_first_scanline)) % stbir_info->ring_buffer_num_entries;
+        STBIR_ASSERT(ring_buffer_index != stbir_info->ring_buffer_begin_index);
+    }
+
+    ring_buffer = stbir__get_ring_buffer_entry(stbir_info->ring_buffer, ring_buffer_index, stbir_info->ring_buffer_length_bytes / sizeof(float));
+    memset(ring_buffer, 0, stbir_info->ring_buffer_length_bytes);
+
+    return ring_buffer;
+}
+
+
+static void stbir__resample_horizontal_upsample(stbir__info* stbir_info, float* output_buffer)
+{
+    int x, k;
+    int output_w = stbir_info->output_w;
+    int channels = stbir_info->channels;
+    float* decode_buffer = stbir__get_decode_buffer(stbir_info);
+    stbir__contributors* horizontal_contributors = stbir_info->horizontal_contributors;
+    float* horizontal_coefficients = stbir_info->horizontal_coefficients;
+    int coefficient_width = stbir_info->horizontal_coefficient_width;
+
+    for (x = 0; x < output_w; x++)
+    {
+        int n0 = horizontal_contributors[x].n0;
+        int n1 = horizontal_contributors[x].n1;
+
+        int out_pixel_index = x * channels;
+        int coefficient_group = coefficient_width * x;
+        int coefficient_counter = 0;
+
+        STBIR_ASSERT(n1 >= n0);
+        STBIR_ASSERT(n0 >= -stbir_info->horizontal_filter_pixel_margin);
+        STBIR_ASSERT(n1 >= -stbir_info->horizontal_filter_pixel_margin);
+        STBIR_ASSERT(n0 < stbir_info->input_w + stbir_info->horizontal_filter_pixel_margin);
+        STBIR_ASSERT(n1 < stbir_info->input_w + stbir_info->horizontal_filter_pixel_margin);
+
+        switch (channels) {
+            case 1:
+                for (k = n0; k <= n1; k++)
+                {
+                    int in_pixel_index = k * 1;
+                    float coefficient = horizontal_coefficients[coefficient_group + coefficient_counter++];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                }
+                break;
+            case 2:
+                for (k = n0; k <= n1; k++)
+                {
+                    int in_pixel_index = k * 2;
+                    float coefficient = horizontal_coefficients[coefficient_group + coefficient_counter++];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                }
+                break;
+            case 3:
+                for (k = n0; k <= n1; k++)
+                {
+                    int in_pixel_index = k * 3;
+                    float coefficient = horizontal_coefficients[coefficient_group + coefficient_counter++];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                    output_buffer[out_pixel_index + 2] += decode_buffer[in_pixel_index + 2] * coefficient;
+                }
+                break;
+            case 4:
+                for (k = n0; k <= n1; k++)
+                {
+                    int in_pixel_index = k * 4;
+                    float coefficient = horizontal_coefficients[coefficient_group + coefficient_counter++];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                    output_buffer[out_pixel_index + 2] += decode_buffer[in_pixel_index + 2] * coefficient;
+                    output_buffer[out_pixel_index + 3] += decode_buffer[in_pixel_index + 3] * coefficient;
+                }
+                break;
+            default:
+                for (k = n0; k <= n1; k++)
+                {
+                    int in_pixel_index = k * channels;
+                    float coefficient = horizontal_coefficients[coefficient_group + coefficient_counter++];
+                    int c;
+                    STBIR_ASSERT(coefficient != 0);
+                    for (c = 0; c < channels; c++)
+                        output_buffer[out_pixel_index + c] += decode_buffer[in_pixel_index + c] * coefficient;
+                }
+                break;
+        }
+    }
+}
+
+static void stbir__resample_horizontal_downsample(stbir__info* stbir_info, float* output_buffer)
+{
+    int x, k;
+    int input_w = stbir_info->input_w;
+    int channels = stbir_info->channels;
+    float* decode_buffer = stbir__get_decode_buffer(stbir_info);
+    stbir__contributors* horizontal_contributors = stbir_info->horizontal_contributors;
+    float* horizontal_coefficients = stbir_info->horizontal_coefficients;
+    int coefficient_width = stbir_info->horizontal_coefficient_width;
+    int filter_pixel_margin = stbir_info->horizontal_filter_pixel_margin;
+    int max_x = input_w + filter_pixel_margin * 2;
+
+    STBIR_ASSERT(!stbir__use_width_upsampling(stbir_info));
+
+    switch (channels) {
+        case 1:
+            for (x = 0; x < max_x; x++)
+            {
+                int n0 = horizontal_contributors[x].n0;
+                int n1 = horizontal_contributors[x].n1;
+
+                int in_x = x - filter_pixel_margin;
+                int in_pixel_index = in_x * 1;
+                int max_n = n1;
+                int coefficient_group = coefficient_width * x;
+
+                for (k = n0; k <= max_n; k++)
+                {
+                    int out_pixel_index = k * 1;
+                    float coefficient = horizontal_coefficients[coefficient_group + k - n0];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                }
+            }
+            break;
+
+        case 2:
+            for (x = 0; x < max_x; x++)
+            {
+                int n0 = horizontal_contributors[x].n0;
+                int n1 = horizontal_contributors[x].n1;
+
+                int in_x = x - filter_pixel_margin;
+                int in_pixel_index = in_x * 2;
+                int max_n = n1;
+                int coefficient_group = coefficient_width * x;
+
+                for (k = n0; k <= max_n; k++)
+                {
+                    int out_pixel_index = k * 2;
+                    float coefficient = horizontal_coefficients[coefficient_group + k - n0];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                }
+            }
+            break;
+
+        case 3:
+            for (x = 0; x < max_x; x++)
+            {
+                int n0 = horizontal_contributors[x].n0;
+                int n1 = horizontal_contributors[x].n1;
+
+                int in_x = x - filter_pixel_margin;
+                int in_pixel_index = in_x * 3;
+                int max_n = n1;
+                int coefficient_group = coefficient_width * x;
+
+                for (k = n0; k <= max_n; k++)
+                {
+                    int out_pixel_index = k * 3;
+                    float coefficient = horizontal_coefficients[coefficient_group + k - n0];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                    output_buffer[out_pixel_index + 2] += decode_buffer[in_pixel_index + 2] * coefficient;
+                }
+            }
+            break;
+
+        case 4:
+            for (x = 0; x < max_x; x++)
+            {
+                int n0 = horizontal_contributors[x].n0;
+                int n1 = horizontal_contributors[x].n1;
+
+                int in_x = x - filter_pixel_margin;
+                int in_pixel_index = in_x * 4;
+                int max_n = n1;
+                int coefficient_group = coefficient_width * x;
+
+                for (k = n0; k <= max_n; k++)
+                {
+                    int out_pixel_index = k * 4;
+                    float coefficient = horizontal_coefficients[coefficient_group + k - n0];
+                    STBIR_ASSERT(coefficient != 0);
+                    output_buffer[out_pixel_index + 0] += decode_buffer[in_pixel_index + 0] * coefficient;
+                    output_buffer[out_pixel_index + 1] += decode_buffer[in_pixel_index + 1] * coefficient;
+                    output_buffer[out_pixel_index + 2] += decode_buffer[in_pixel_index + 2] * coefficient;
+                    output_buffer[out_pixel_index + 3] += decode_buffer[in_pixel_index + 3] * coefficient;
+                }
+            }
+            break;
+
+        default:
+            for (x = 0; x < max_x; x++)
+            {
+                int n0 = horizontal_contributors[x].n0;
+                int n1 = horizontal_contributors[x].n1;
+
+                int in_x = x - filter_pixel_margin;
+                int in_pixel_index = in_x * channels;
+                int max_n = n1;
+                int coefficient_group = coefficient_width * x;
+
+                for (k = n0; k <= max_n; k++)
+                {
+                    int c;
+                    int out_pixel_index = k * channels;
+                    float coefficient = horizontal_coefficients[coefficient_group + k - n0];
+                    STBIR_ASSERT(coefficient != 0);
+                    for (c = 0; c < channels; c++)
+                        output_buffer[out_pixel_index + c] += decode_buffer[in_pixel_index + c] * coefficient;
+                }
+            }
+            break;
+    }
+}
+
+static void stbir__decode_and_resample_upsample(stbir__info* stbir_info, int n)
+{
+    // Decode the nth scanline from the source image into the decode buffer.
+    stbir__decode_scanline(stbir_info, n);
+
+    // Now resample it into the ring buffer.
+    if (stbir__use_width_upsampling(stbir_info))
+        stbir__resample_horizontal_upsample(stbir_info, stbir__add_empty_ring_buffer_entry(stbir_info, n));
+    else
+        stbir__resample_horizontal_downsample(stbir_info, stbir__add_empty_ring_buffer_entry(stbir_info, n));
+
+    // Now it's sitting in the ring buffer ready to be used as source for the vertical sampling.
+}
+
+static void stbir__decode_and_resample_downsample(stbir__info* stbir_info, int n)
+{
+    // Decode the nth scanline from the source image into the decode buffer.
+    stbir__decode_scanline(stbir_info, n);
+
+    memset(stbir_info->horizontal_buffer, 0, stbir_info->output_w * stbir_info->channels * sizeof(float));
+
+    // Now resample it into the horizontal buffer.
+    if (stbir__use_width_upsampling(stbir_info))
+        stbir__resample_horizontal_upsample(stbir_info, stbir_info->horizontal_buffer);
+    else
+        stbir__resample_horizontal_downsample(stbir_info, stbir_info->horizontal_buffer);
+
+    // Now it's sitting in the horizontal buffer ready to be distributed into the ring buffers.
+}
+
+// Get the specified scan line from the ring buffer.
+static float* stbir__get_ring_buffer_scanline(int get_scanline, float* ring_buffer, int begin_index, int first_scanline, int ring_buffer_num_entries, int ring_buffer_length)
+{
+    int ring_buffer_index = (begin_index + (get_scanline - first_scanline)) % ring_buffer_num_entries;
+    return stbir__get_ring_buffer_entry(ring_buffer, ring_buffer_index, ring_buffer_length);
+}
+
+
+static void stbir__encode_scanline(stbir__info* stbir_info, int num_pixels, void *output_buffer, float *encode_buffer, int channels, int alpha_channel, int decode)
+{
+    int x;
+    int n;
+    int num_nonalpha;
+    stbir_uint16 nonalpha[STBIR_MAX_CHANNELS];
+
+    if (!(stbir_info->flags&STBIR_FLAG_ALPHA_PREMULTIPLIED))
+    {
+        for (x=0; x < num_pixels; ++x)
+        {
+            int pixel_index = x*channels;
+
+            float alpha = encode_buffer[pixel_index + alpha_channel];
+            float reciprocal_alpha = alpha ? 1.0f / alpha : 0;
+
+            // unrolling this produced a 1% slowdown upscaling a large RGBA linear-space image on my machine - stb
+            for (n = 0; n < channels; n++)
+                if (n != alpha_channel)
+                    encode_buffer[pixel_index + n] *= reciprocal_alpha;
+
+            // We added in a small epsilon to prevent the color channel from being deleted with zero alpha.
+            // Because we only add it for integer types, it will automatically be discarded on integer
+            // conversion, so we don't need to subtract it back out (which would be problematic for
+            // numeric precision reasons).
+        }
+    }
+
+    // build a table of all channels that need colorspace correction, so
+    // we don't perform colorspace correction on channels that don't need it.
+    for (x = 0, num_nonalpha = 0; x < channels; ++x)
+    {
+        if (x != alpha_channel || (stbir_info->flags & STBIR_FLAG_ALPHA_USES_COLORSPACE))
+        {
+            nonalpha[num_nonalpha++] = (stbir_uint16)x;
+        }
+    }
+
+    #define STBIR__ROUND_INT(f)    ((int)          ((f)+0.5))
+    #define STBIR__ROUND_UINT(f)   ((stbir_uint32) ((f)+0.5))
+
+    #ifdef STBIR__SATURATE_INT
+    #define STBIR__ENCODE_LINEAR8(f)   stbir__saturate8 (STBIR__ROUND_INT((f) * stbir__max_uint8_as_float ))
+    #define STBIR__ENCODE_LINEAR16(f)  stbir__saturate16(STBIR__ROUND_INT((f) * stbir__max_uint16_as_float))
+    #else
+    #define STBIR__ENCODE_LINEAR8(f)   (unsigned char ) STBIR__ROUND_INT(stbir__saturate(f) * stbir__max_uint8_as_float )
+    #define STBIR__ENCODE_LINEAR16(f)  (unsigned short) STBIR__ROUND_INT(stbir__saturate(f) * stbir__max_uint16_as_float)
+    #endif
+
+    switch (decode)
+    {
+        case STBIR__DECODE(STBIR_TYPE_UINT8, STBIR_COLORSPACE_LINEAR):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < channels; n++)
+                {
+                    int index = pixel_index + n;
+                    ((unsigned char*)output_buffer)[index] = STBIR__ENCODE_LINEAR8(encode_buffer[index]);
+                }
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_UINT8, STBIR_COLORSPACE_SRGB):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < num_nonalpha; n++)
+                {
+                    int index = pixel_index + nonalpha[n];
+                    ((unsigned char*)output_buffer)[index] = stbir__linear_to_srgb_uchar(encode_buffer[index]);
+                }
+
+                if (!(stbir_info->flags & STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                    ((unsigned char *)output_buffer)[pixel_index + alpha_channel] = STBIR__ENCODE_LINEAR8(encode_buffer[pixel_index+alpha_channel]);
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_UINT16, STBIR_COLORSPACE_LINEAR):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < channels; n++)
+                {
+                    int index = pixel_index + n;
+                    ((unsigned short*)output_buffer)[index] = STBIR__ENCODE_LINEAR16(encode_buffer[index]);
+                }
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_UINT16, STBIR_COLORSPACE_SRGB):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < num_nonalpha; n++)
+                {
+                    int index = pixel_index + nonalpha[n];
+                    ((unsigned short*)output_buffer)[index] = (unsigned short)STBIR__ROUND_INT(stbir__linear_to_srgb(stbir__saturate(encode_buffer[index])) * stbir__max_uint16_as_float);
+                }
+
+                if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                    ((unsigned short*)output_buffer)[pixel_index + alpha_channel] = STBIR__ENCODE_LINEAR16(encode_buffer[pixel_index + alpha_channel]);
+            }
+
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_UINT32, STBIR_COLORSPACE_LINEAR):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < channels; n++)
+                {
+                    int index = pixel_index + n;
+                    ((unsigned int*)output_buffer)[index] = (unsigned int)STBIR__ROUND_UINT(((double)stbir__saturate(encode_buffer[index])) * stbir__max_uint32_as_float);
+                }
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_UINT32, STBIR_COLORSPACE_SRGB):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < num_nonalpha; n++)
+                {
+                    int index = pixel_index + nonalpha[n];
+                    ((unsigned int*)output_buffer)[index] = (unsigned int)STBIR__ROUND_UINT(((double)stbir__linear_to_srgb(stbir__saturate(encode_buffer[index]))) * stbir__max_uint32_as_float);
+                }
+
+                if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                    ((unsigned int*)output_buffer)[pixel_index + alpha_channel] = (unsigned int)STBIR__ROUND_INT(((double)stbir__saturate(encode_buffer[pixel_index + alpha_channel])) * stbir__max_uint32_as_float);
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_FLOAT, STBIR_COLORSPACE_LINEAR):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < channels; n++)
+                {
+                    int index = pixel_index + n;
+                    ((float*)output_buffer)[index] = encode_buffer[index];
+                }
+            }
+            break;
+
+        case STBIR__DECODE(STBIR_TYPE_FLOAT, STBIR_COLORSPACE_SRGB):
+            for (x=0; x < num_pixels; ++x)
+            {
+                int pixel_index = x*channels;
+
+                for (n = 0; n < num_nonalpha; n++)
+                {
+                    int index = pixel_index + nonalpha[n];
+                    ((float*)output_buffer)[index] = stbir__linear_to_srgb(encode_buffer[index]);
+                }
+
+                if (!(stbir_info->flags&STBIR_FLAG_ALPHA_USES_COLORSPACE))
+                    ((float*)output_buffer)[pixel_index + alpha_channel] = encode_buffer[pixel_index + alpha_channel];
+            }
+            break;
+
+        default:
+            STBIR_ASSERT(!"Unknown type/colorspace/channels combination.");
+            break;
+    }
+}
+
+static void stbir__resample_vertical_upsample(stbir__info* stbir_info, int n)
+{
+    int x, k;
+    int output_w = stbir_info->output_w;
+    stbir__contributors* vertical_contributors = stbir_info->vertical_contributors;
+    float* vertical_coefficients = stbir_info->vertical_coefficients;
+    int channels = stbir_info->channels;
+    int alpha_channel = stbir_info->alpha_channel;
+    int type = stbir_info->type;
+    int colorspace = stbir_info->colorspace;
+    int ring_buffer_entries = stbir_info->ring_buffer_num_entries;
+    void* output_data = stbir_info->output_data;
+    float* encode_buffer = stbir_info->encode_buffer;
+    int decode = STBIR__DECODE(type, colorspace);
+    int coefficient_width = stbir_info->vertical_coefficient_width;
+    int coefficient_counter;
+    int contributor = n;
+
+    float* ring_buffer = stbir_info->ring_buffer;
+    int ring_buffer_begin_index = stbir_info->ring_buffer_begin_index;
+    int ring_buffer_first_scanline = stbir_info->ring_buffer_first_scanline;
+    int ring_buffer_length = stbir_info->ring_buffer_length_bytes/sizeof(float);
+
+    int n0,n1, output_row_start;
+    int coefficient_group = coefficient_width * contributor;
+
+    n0 = vertical_contributors[contributor].n0;
+    n1 = vertical_contributors[contributor].n1;
+
+    output_row_start = n * stbir_info->output_stride_bytes;
+
+    STBIR_ASSERT(stbir__use_height_upsampling(stbir_info));
+
+    memset(encode_buffer, 0, output_w * sizeof(float) * channels);
+
+    // I tried reblocking this for better cache usage of encode_buffer
+    // (using x_outer, k, x_inner), but it lost speed. -- stb
+
+    coefficient_counter = 0;
+    switch (channels) {
+        case 1:
+            for (k = n0; k <= n1; k++)
+            {
+                int coefficient_index = coefficient_counter++;
+                float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+                float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+                for (x = 0; x < output_w; ++x)
+                {
+                    int in_pixel_index = x * 1;
+                    encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
+                }
+            }
+            break;
+        case 2:
+            for (k = n0; k <= n1; k++)
+            {
+                int coefficient_index = coefficient_counter++;
+                float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+                float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+                for (x = 0; x < output_w; ++x)
+                {
+                    int in_pixel_index = x * 2;
+                    encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
+                    encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
+                }
+            }
+            break;
+        case 3:
+            for (k = n0; k <= n1; k++)
+            {
+                int coefficient_index = coefficient_counter++;
+                float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+                float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+                for (x = 0; x < output_w; ++x)
+                {
+                    int in_pixel_index = x * 3;
+                    encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
+                    encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
+                    encode_buffer[in_pixel_index + 2] += ring_buffer_entry[in_pixel_index + 2] * coefficient;
+                }
+            }
+            break;
+        case 4:
+            for (k = n0; k <= n1; k++)
+            {
+                int coefficient_index = coefficient_counter++;
+                float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+                float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+                for (x = 0; x < output_w; ++x)
+                {
+                    int in_pixel_index = x * 4;
+                    encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
+                    encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
+                    encode_buffer[in_pixel_index + 2] += ring_buffer_entry[in_pixel_index + 2] * coefficient;
+                    encode_buffer[in_pixel_index + 3] += ring_buffer_entry[in_pixel_index + 3] * coefficient;
+                }
+            }
+            break;
+        default:
+            for (k = n0; k <= n1; k++)
+            {
+                int coefficient_index = coefficient_counter++;
+                float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+                float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+                for (x = 0; x < output_w; ++x)
+                {
+                    int in_pixel_index = x * channels;
+                    int c;
+                    for (c = 0; c < channels; c++)
+                        encode_buffer[in_pixel_index + c] += ring_buffer_entry[in_pixel_index + c] * coefficient;
+                }
+            }
+            break;
+    }
+    stbir__encode_scanline(stbir_info, output_w, (char *) output_data + output_row_start, encode_buffer, channels, alpha_channel, decode);
+}
+
+static void stbir__resample_vertical_downsample(stbir__info* stbir_info, int n)
+{
+    int x, k;
+    int output_w = stbir_info->output_w;
+    stbir__contributors* vertical_contributors = stbir_info->vertical_contributors;
+    float* vertical_coefficients = stbir_info->vertical_coefficients;
+    int channels = stbir_info->channels;
+    int ring_buffer_entries = stbir_info->ring_buffer_num_entries;
+    float* horizontal_buffer = stbir_info->horizontal_buffer;
+    int coefficient_width = stbir_info->vertical_coefficient_width;
+    int contributor = n + stbir_info->vertical_filter_pixel_margin;
+
+    float* ring_buffer = stbir_info->ring_buffer;
+    int ring_buffer_begin_index = stbir_info->ring_buffer_begin_index;
+    int ring_buffer_first_scanline = stbir_info->ring_buffer_first_scanline;
+    int ring_buffer_length = stbir_info->ring_buffer_length_bytes/sizeof(float);
+    int n0,n1;
+
+    n0 = vertical_contributors[contributor].n0;
+    n1 = vertical_contributors[contributor].n1;
+
+    STBIR_ASSERT(!stbir__use_height_upsampling(stbir_info));
+
+    for (k = n0; k <= n1; k++)
+    {
+        int coefficient_index = k - n0;
+        int coefficient_group = coefficient_width * contributor;
+        float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
+
+        float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, ring_buffer_entries, ring_buffer_length);
+
+        switch (channels) {
+            case 1:
+                for (x = 0; x < output_w; x++)
+                {
+                    int in_pixel_index = x * 1;
+                    ring_buffer_entry[in_pixel_index + 0] += horizontal_buffer[in_pixel_index + 0] * coefficient;
+                }
+                break;
+            case 2:
+                for (x = 0; x < output_w; x++)
+                {
+                    int in_pixel_index = x * 2;
+                    ring_buffer_entry[in_pixel_index + 0] += horizontal_buffer[in_pixel_index + 0] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 1] += horizontal_buffer[in_pixel_index + 1] * coefficient;
+                }
+                break;
+            case 3:
+                for (x = 0; x < output_w; x++)
+                {
+                    int in_pixel_index = x * 3;
+                    ring_buffer_entry[in_pixel_index + 0] += horizontal_buffer[in_pixel_index + 0] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 1] += horizontal_buffer[in_pixel_index + 1] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 2] += horizontal_buffer[in_pixel_index + 2] * coefficient;
+                }
+                break;
+            case 4:
+                for (x = 0; x < output_w; x++)
+                {
+                    int in_pixel_index = x * 4;
+                    ring_buffer_entry[in_pixel_index + 0] += horizontal_buffer[in_pixel_index + 0] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 1] += horizontal_buffer[in_pixel_index + 1] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 2] += horizontal_buffer[in_pixel_index + 2] * coefficient;
+                    ring_buffer_entry[in_pixel_index + 3] += horizontal_buffer[in_pixel_index + 3] * coefficient;
+                }
+                break;
+            default:
+                for (x = 0; x < output_w; x++)
+                {
+                    int in_pixel_index = x * channels;
+
+                    int c;
+                    for (c = 0; c < channels; c++)
+                        ring_buffer_entry[in_pixel_index + c] += horizontal_buffer[in_pixel_index + c] * coefficient;
+                }
+                break;
+        }
+    }
+}
+
+static void stbir__buffer_loop_upsample(stbir__info* stbir_info)
+{
+    int y;
+    float scale_ratio = stbir_info->vertical_scale;
+    float out_scanlines_radius = stbir__filter_info_table[stbir_info->vertical_filter].support(1/scale_ratio) * scale_ratio;
+
+    STBIR_ASSERT(stbir__use_height_upsampling(stbir_info));
+
+    for (y = 0; y < stbir_info->output_h; y++)
+    {
+        float in_center_of_out = 0; // Center of the current out scanline in the in scanline space
+        int in_first_scanline = 0, in_last_scanline = 0;
+
+        stbir__calculate_sample_range_upsample(y, out_scanlines_radius, scale_ratio, stbir_info->vertical_shift, &in_first_scanline, &in_last_scanline, &in_center_of_out);
+
+        STBIR_ASSERT(in_last_scanline - in_first_scanline + 1 <= stbir_info->ring_buffer_num_entries);
+
+        if (stbir_info->ring_buffer_begin_index >= 0)
+        {
+            // Get rid of whatever we don't need anymore.
+            while (in_first_scanline > stbir_info->ring_buffer_first_scanline)
+            {
+                if (stbir_info->ring_buffer_first_scanline == stbir_info->ring_buffer_last_scanline)
+                {
+                    // We just popped the last scanline off the ring buffer.
+                    // Reset it to the empty state.
+                    stbir_info->ring_buffer_begin_index = -1;
+                    stbir_info->ring_buffer_first_scanline = 0;
+                    stbir_info->ring_buffer_last_scanline = 0;
+                    break;
+                }
+                else
+                {
+                    stbir_info->ring_buffer_first_scanline++;
+                    stbir_info->ring_buffer_begin_index = (stbir_info->ring_buffer_begin_index + 1) % stbir_info->ring_buffer_num_entries;
+                }
+            }
+        }
+
+        // Load in new ones.
+        if (stbir_info->ring_buffer_begin_index < 0)
+            stbir__decode_and_resample_upsample(stbir_info, in_first_scanline);
+
+        while (in_last_scanline > stbir_info->ring_buffer_last_scanline)
+            stbir__decode_and_resample_upsample(stbir_info, stbir_info->ring_buffer_last_scanline + 1);
+
+        // Now all buffers should be ready to write a row of vertical sampling.
+        stbir__resample_vertical_upsample(stbir_info, y);
+
+        STBIR_PROGRESS_REPORT((float)y / stbir_info->output_h);
+    }
+}
+
+static void stbir__empty_ring_buffer(stbir__info* stbir_info, int first_necessary_scanline)
+{
+    int output_stride_bytes = stbir_info->output_stride_bytes;
+    int channels = stbir_info->channels;
+    int alpha_channel = stbir_info->alpha_channel;
+    int type = stbir_info->type;
+    int colorspace = stbir_info->colorspace;
+    int output_w = stbir_info->output_w;
+    void* output_data = stbir_info->output_data;
+    int decode = STBIR__DECODE(type, colorspace);
+
+    float* ring_buffer = stbir_info->ring_buffer;
+    int ring_buffer_length = stbir_info->ring_buffer_length_bytes/sizeof(float);
+
+    if (stbir_info->ring_buffer_begin_index >= 0)
+    {
+        // Get rid of whatever we don't need anymore.
+        while (first_necessary_scanline > stbir_info->ring_buffer_first_scanline)
+        {
+            if (stbir_info->ring_buffer_first_scanline >= 0 && stbir_info->ring_buffer_first_scanline < stbir_info->output_h)
+            {
+                int output_row_start = stbir_info->ring_buffer_first_scanline * output_stride_bytes;
+                float* ring_buffer_entry = stbir__get_ring_buffer_entry(ring_buffer, stbir_info->ring_buffer_begin_index, ring_buffer_length);
+                stbir__encode_scanline(stbir_info, output_w, (char *) output_data + output_row_start, ring_buffer_entry, channels, alpha_channel, decode);
+                STBIR_PROGRESS_REPORT((float)stbir_info->ring_buffer_first_scanline / stbir_info->output_h);
+            }
+
+            if (stbir_info->ring_buffer_first_scanline == stbir_info->ring_buffer_last_scanline)
+            {
+                // We just popped the last scanline off the ring buffer.
+                // Reset it to the empty state.
+                stbir_info->ring_buffer_begin_index = -1;
+                stbir_info->ring_buffer_first_scanline = 0;
+                stbir_info->ring_buffer_last_scanline = 0;
+                break;
+            }
+            else
+            {
+                stbir_info->ring_buffer_first_scanline++;
+                stbir_info->ring_buffer_begin_index = (stbir_info->ring_buffer_begin_index + 1) % stbir_info->ring_buffer_num_entries;
+            }
+        }
+    }
+}
+
+static void stbir__buffer_loop_downsample(stbir__info* stbir_info)
+{
+    int y;
+    float scale_ratio = stbir_info->vertical_scale;
+    int output_h = stbir_info->output_h;
+    float in_pixels_radius = stbir__filter_info_table[stbir_info->vertical_filter].support(scale_ratio) / scale_ratio;
+    int pixel_margin = stbir_info->vertical_filter_pixel_margin;
+    int max_y = stbir_info->input_h + pixel_margin;
+
+    STBIR_ASSERT(!stbir__use_height_upsampling(stbir_info));
+
+    for (y = -pixel_margin; y < max_y; y++)
+    {
+        float out_center_of_in; // Center of the current out scanline in the in scanline space
+        int out_first_scanline, out_last_scanline;
+
+        stbir__calculate_sample_range_downsample(y, in_pixels_radius, scale_ratio, stbir_info->vertical_shift, &out_first_scanline, &out_last_scanline, &out_center_of_in);
+
+        STBIR_ASSERT(out_last_scanline - out_first_scanline + 1 <= stbir_info->ring_buffer_num_entries);
+
+        if (out_last_scanline < 0 || out_first_scanline >= output_h)
+            continue;
+
+        stbir__empty_ring_buffer(stbir_info, out_first_scanline);
+
+        stbir__decode_and_resample_downsample(stbir_info, y);
+
+        // Load in new ones.
+        if (stbir_info->ring_buffer_begin_index < 0)
+            stbir__add_empty_ring_buffer_entry(stbir_info, out_first_scanline);
+
+        while (out_last_scanline > stbir_info->ring_buffer_last_scanline)
+            stbir__add_empty_ring_buffer_entry(stbir_info, stbir_info->ring_buffer_last_scanline + 1);
+
+        // Now the horizontal buffer is ready to write to all ring buffer rows.
+        stbir__resample_vertical_downsample(stbir_info, y);
+    }
+
+    stbir__empty_ring_buffer(stbir_info, stbir_info->output_h);
+}
+
+static void stbir__setup(stbir__info *info, int input_w, int input_h, int output_w, int output_h, int channels)
+{
+    info->input_w = input_w;
+    info->input_h = input_h;
+    info->output_w = output_w;
+    info->output_h = output_h;
+    info->channels = channels;
+}
+
+static void stbir__calculate_transform(stbir__info *info, float s0, float t0, float s1, float t1, float *transform)
+{
+    info->s0 = s0;
+    info->t0 = t0;
+    info->s1 = s1;
+    info->t1 = t1;
+
+    if (transform)
+    {
+        info->horizontal_scale = transform[0];
+        info->vertical_scale   = transform[1];
+        info->horizontal_shift = transform[2];
+        info->vertical_shift   = transform[3];
+    }
+    else
+    {
+        info->horizontal_scale = ((float)info->output_w / info->input_w) / (s1 - s0);
+        info->vertical_scale = ((float)info->output_h / info->input_h) / (t1 - t0);
+
+        info->horizontal_shift = s0 * info->output_w / (s1 - s0);
+        info->vertical_shift = t0 * info->output_h / (t1 - t0);
+    }
+}
+
+static void stbir__choose_filter(stbir__info *info, stbir_filter h_filter, stbir_filter v_filter)
+{
+    if (h_filter == 0)
+        h_filter = stbir__use_upsampling(info->horizontal_scale) ? STBIR_DEFAULT_FILTER_UPSAMPLE : STBIR_DEFAULT_FILTER_DOWNSAMPLE;
+    if (v_filter == 0)
+        v_filter = stbir__use_upsampling(info->vertical_scale)   ? STBIR_DEFAULT_FILTER_UPSAMPLE : STBIR_DEFAULT_FILTER_DOWNSAMPLE;
+    info->horizontal_filter = h_filter;
+    info->vertical_filter = v_filter;
+}
+
+static stbir_uint32 stbir__calculate_memory(stbir__info *info)
+{
+    int pixel_margin = stbir__get_filter_pixel_margin(info->horizontal_filter, info->horizontal_scale);
+    int filter_height = stbir__get_filter_pixel_width(info->vertical_filter, info->vertical_scale);
+
+    info->horizontal_num_contributors = stbir__get_contributors(info->horizontal_scale, info->horizontal_filter, info->input_w, info->output_w);
+    info->vertical_num_contributors   = stbir__get_contributors(info->vertical_scale  , info->vertical_filter  , info->input_h, info->output_h);
+
+    // One extra entry because floating point precision problems sometimes cause an extra to be necessary.
+    info->ring_buffer_num_entries = filter_height + 1;
+
+    info->horizontal_contributors_size = info->horizontal_num_contributors * sizeof(stbir__contributors);
+    info->horizontal_coefficients_size = stbir__get_total_horizontal_coefficients(info) * sizeof(float);
+    info->vertical_contributors_size = info->vertical_num_contributors * sizeof(stbir__contributors);
+    info->vertical_coefficients_size = stbir__get_total_vertical_coefficients(info) * sizeof(float);
+    info->decode_buffer_size = (info->input_w + pixel_margin * 2) * info->channels * sizeof(float);
+    info->horizontal_buffer_size = info->output_w * info->channels * sizeof(float);
+    info->ring_buffer_size = info->output_w * info->channels * info->ring_buffer_num_entries * sizeof(float);
+    info->encode_buffer_size = info->output_w * info->channels * sizeof(float);
+
+    STBIR_ASSERT(info->horizontal_filter != 0);
+    STBIR_ASSERT(info->horizontal_filter < STBIR__ARRAY_SIZE(stbir__filter_info_table)); // this now happens too late
+    STBIR_ASSERT(info->vertical_filter != 0);
+    STBIR_ASSERT(info->vertical_filter < STBIR__ARRAY_SIZE(stbir__filter_info_table)); // this now happens too late
+
+    if (stbir__use_height_upsampling(info))
+        // The horizontal buffer is for when we're downsampling the height and we
+        // can't output the result of sampling the decode buffer directly into the
+        // ring buffers.
+        info->horizontal_buffer_size = 0;
+    else
+        // The encode buffer is to retain precision in the height upsampling method
+        // and isn't used when height downsampling.
+        info->encode_buffer_size = 0;
+
+    return info->horizontal_contributors_size + info->horizontal_coefficients_size
+        + info->vertical_contributors_size + info->vertical_coefficients_size
+        + info->decode_buffer_size + info->horizontal_buffer_size
+        + info->ring_buffer_size + info->encode_buffer_size;
+}
+
+static int stbir__resize_allocated(stbir__info *info,
+    const void* input_data, int input_stride_in_bytes,
+    void* output_data, int output_stride_in_bytes,
+    int alpha_channel, stbir_uint32 flags, stbir_datatype type,
+    stbir_edge edge_horizontal, stbir_edge edge_vertical, stbir_colorspace colorspace,
+    void* tempmem, size_t tempmem_size_in_bytes)
+{
+    size_t memory_required = stbir__calculate_memory(info);
+
+    int width_stride_input = input_stride_in_bytes ? input_stride_in_bytes : info->channels * info->input_w * stbir__type_size[type];
+    int width_stride_output = output_stride_in_bytes ? output_stride_in_bytes : info->channels * info->output_w * stbir__type_size[type];
+
+#ifdef STBIR_DEBUG_OVERWRITE_TEST
+#define OVERWRITE_ARRAY_SIZE 8
+    unsigned char overwrite_output_before_pre[OVERWRITE_ARRAY_SIZE];
+    unsigned char overwrite_tempmem_before_pre[OVERWRITE_ARRAY_SIZE];
+    unsigned char overwrite_output_after_pre[OVERWRITE_ARRAY_SIZE];
+    unsigned char overwrite_tempmem_after_pre[OVERWRITE_ARRAY_SIZE];
+
+    size_t begin_forbidden = width_stride_output * (info->output_h - 1) + info->output_w * info->channels * stbir__type_size[type];
+    memcpy(overwrite_output_before_pre, &((unsigned char*)output_data)[-OVERWRITE_ARRAY_SIZE], OVERWRITE_ARRAY_SIZE);
+    memcpy(overwrite_output_after_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE);
+    memcpy(overwrite_tempmem_before_pre, &((unsigned char*)tempmem)[-OVERWRITE_ARRAY_SIZE], OVERWRITE_ARRAY_SIZE);
+    memcpy(overwrite_tempmem_after_pre, &((unsigned char*)tempmem)[tempmem_size_in_bytes], OVERWRITE_ARRAY_SIZE);
+#endif
+
+    STBIR_ASSERT(info->channels >= 0);
+    STBIR_ASSERT(info->channels <= STBIR_MAX_CHANNELS);
+
+    if (info->channels < 0 || info->channels > STBIR_MAX_CHANNELS)
+        return 0;
+
+    STBIR_ASSERT(info->horizontal_filter < STBIR__ARRAY_SIZE(stbir__filter_info_table));
+    STBIR_ASSERT(info->vertical_filter < STBIR__ARRAY_SIZE(stbir__filter_info_table));
+
+    if (info->horizontal_filter >= STBIR__ARRAY_SIZE(stbir__filter_info_table))
+        return 0;
+    if (info->vertical_filter >= STBIR__ARRAY_SIZE(stbir__filter_info_table))
+        return 0;
+
+    if (alpha_channel < 0)
+        flags |= STBIR_FLAG_ALPHA_USES_COLORSPACE | STBIR_FLAG_ALPHA_PREMULTIPLIED;
+
+    if (!(flags&STBIR_FLAG_ALPHA_USES_COLORSPACE) || !(flags&STBIR_FLAG_ALPHA_PREMULTIPLIED)) {
+        STBIR_ASSERT(alpha_channel >= 0 && alpha_channel < info->channels);
+    }
+
+    if (alpha_channel >= info->channels)
+        return 0;
+
+    STBIR_ASSERT(tempmem);
+
+    if (!tempmem)
+        return 0;
+
+    STBIR_ASSERT(tempmem_size_in_bytes >= memory_required);
+
+    if (tempmem_size_in_bytes < memory_required)
+        return 0;
+
+    memset(tempmem, 0, tempmem_size_in_bytes);
+
+    info->input_data = input_data;
+    info->input_stride_bytes = width_stride_input;
+
+    info->output_data = output_data;
+    info->output_stride_bytes = width_stride_output;
+
+    info->alpha_channel = alpha_channel;
+    info->flags = flags;
+    info->type = type;
+    info->edge_horizontal = edge_horizontal;
+    info->edge_vertical = edge_vertical;
+    info->colorspace = colorspace;
+
+    info->horizontal_coefficient_width   = stbir__get_coefficient_width  (info->horizontal_filter, info->horizontal_scale);
+    info->vertical_coefficient_width     = stbir__get_coefficient_width  (info->vertical_filter  , info->vertical_scale  );
+    info->horizontal_filter_pixel_width  = stbir__get_filter_pixel_width (info->horizontal_filter, info->horizontal_scale);
+    info->vertical_filter_pixel_width    = stbir__get_filter_pixel_width (info->vertical_filter  , info->vertical_scale  );
+    info->horizontal_filter_pixel_margin = stbir__get_filter_pixel_margin(info->horizontal_filter, info->horizontal_scale);
+    info->vertical_filter_pixel_margin   = stbir__get_filter_pixel_margin(info->vertical_filter  , info->vertical_scale  );
+
+    info->ring_buffer_length_bytes = info->output_w * info->channels * sizeof(float);
+    info->decode_buffer_pixels = info->input_w + info->horizontal_filter_pixel_margin * 2;
+
+#define STBIR__NEXT_MEMPTR(current, newtype) (newtype*)(((unsigned char*)current) + current##_size)
+
+    info->horizontal_contributors = (stbir__contributors *) tempmem;
+    info->horizontal_coefficients = STBIR__NEXT_MEMPTR(info->horizontal_contributors, float);
+    info->vertical_contributors = STBIR__NEXT_MEMPTR(info->horizontal_coefficients, stbir__contributors);
+    info->vertical_coefficients = STBIR__NEXT_MEMPTR(info->vertical_contributors, float);
+    info->decode_buffer = STBIR__NEXT_MEMPTR(info->vertical_coefficients, float);
+
+    if (stbir__use_height_upsampling(info))
+    {
+        info->horizontal_buffer = NULL;
+        info->ring_buffer = STBIR__NEXT_MEMPTR(info->decode_buffer, float);
+        info->encode_buffer = STBIR__NEXT_MEMPTR(info->ring_buffer, float);
+
+        STBIR_ASSERT((size_t)STBIR__NEXT_MEMPTR(info->encode_buffer, unsigned char) == (size_t)tempmem + tempmem_size_in_bytes);
+    }
+    else
+    {
+        info->horizontal_buffer = STBIR__NEXT_MEMPTR(info->decode_buffer, float);
+        info->ring_buffer = STBIR__NEXT_MEMPTR(info->horizontal_buffer, float);
+        info->encode_buffer = NULL;
+
+        STBIR_ASSERT((size_t)STBIR__NEXT_MEMPTR(info->ring_buffer, unsigned char) == (size_t)tempmem + tempmem_size_in_bytes);
+    }
+
+#undef STBIR__NEXT_MEMPTR
+
+    // This signals that the ring buffer is empty
+    info->ring_buffer_begin_index = -1;
+
+    stbir__calculate_filters(info->horizontal_contributors, info->horizontal_coefficients, info->horizontal_filter, info->horizontal_scale, info->horizontal_shift, info->input_w, info->output_w);
+    stbir__calculate_filters(info->vertical_contributors, info->vertical_coefficients, info->vertical_filter, info->vertical_scale, info->vertical_shift, info->input_h, info->output_h);
+
+    STBIR_PROGRESS_REPORT(0);
+
+    if (stbir__use_height_upsampling(info))
+        stbir__buffer_loop_upsample(info);
+    else
+        stbir__buffer_loop_downsample(info);
+
+    STBIR_PROGRESS_REPORT(1);
+
+#ifdef STBIR_DEBUG_OVERWRITE_TEST
+    STBIR_ASSERT(memcmp(overwrite_output_before_pre, &((unsigned char*)output_data)[-OVERWRITE_ARRAY_SIZE], OVERWRITE_ARRAY_SIZE) == 0);
+    STBIR_ASSERT(memcmp(overwrite_output_after_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE) == 0);
+    STBIR_ASSERT(memcmp(overwrite_tempmem_before_pre, &((unsigned char*)tempmem)[-OVERWRITE_ARRAY_SIZE], OVERWRITE_ARRAY_SIZE) == 0);
+    STBIR_ASSERT(memcmp(overwrite_tempmem_after_pre, &((unsigned char*)tempmem)[tempmem_size_in_bytes], OVERWRITE_ARRAY_SIZE) == 0);
+#endif
+
+    return 1;
+}
+
+
+static int stbir__resize_arbitrary(
+    void *alloc_context,
+    const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
+    void* output_data, int output_w, int output_h, int output_stride_in_bytes,
+    float s0, float t0, float s1, float t1, float *transform,
+    int channels, int alpha_channel, stbir_uint32 flags, stbir_datatype type,
+    stbir_filter h_filter, stbir_filter v_filter,
+    stbir_edge edge_horizontal, stbir_edge edge_vertical, stbir_colorspace colorspace)
+{
+    stbir__info info;
+    int result;
+    size_t memory_required;
+    void* extra_memory;
+
+    stbir__setup(&info, input_w, input_h, output_w, output_h, channels);
+    stbir__calculate_transform(&info, s0,t0,s1,t1,transform);
+    stbir__choose_filter(&info, h_filter, v_filter);
+    memory_required = stbir__calculate_memory(&info);
+    extra_memory = STBIR_MALLOC(memory_required, alloc_context);
+
+    if (!extra_memory)
+        return 0;
+
+    result = stbir__resize_allocated(&info, input_data, input_stride_in_bytes,
+                                            output_data, output_stride_in_bytes,
+                                            alpha_channel, flags, type,
+                                            edge_horizontal, edge_vertical,
+                                            colorspace, extra_memory, memory_required);
+
+    STBIR_FREE(extra_memory, alloc_context);
+
+    return result;
+}
+
+STBIRDEF int stbir_resize_uint8(     const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels)
+{
+    return stbir__resize_arbitrary(NULL, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,-1,0, STBIR_TYPE_UINT8, STBIR_FILTER_DEFAULT, STBIR_FILTER_DEFAULT,
+        STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP, STBIR_COLORSPACE_LINEAR);
+}
+
+STBIRDEF int stbir_resize_float(     const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           float *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels)
+{
+    return stbir__resize_arbitrary(NULL, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,-1,0, STBIR_TYPE_FLOAT, STBIR_FILTER_DEFAULT, STBIR_FILTER_DEFAULT,
+        STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP, STBIR_COLORSPACE_LINEAR);
+}
+
+STBIRDEF int stbir_resize_uint8_srgb(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                           unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                     int num_channels, int alpha_channel, int flags)
+{
+    return stbir__resize_arbitrary(NULL, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, STBIR_TYPE_UINT8, STBIR_FILTER_DEFAULT, STBIR_FILTER_DEFAULT,
+        STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP, STBIR_COLORSPACE_SRGB);
+}
+
+STBIRDEF int stbir_resize_uint8_srgb_edgemode(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                                    unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                              int num_channels, int alpha_channel, int flags,
+                                              stbir_edge edge_wrap_mode)
+{
+    return stbir__resize_arbitrary(NULL, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, STBIR_TYPE_UINT8, STBIR_FILTER_DEFAULT, STBIR_FILTER_DEFAULT,
+        edge_wrap_mode, edge_wrap_mode, STBIR_COLORSPACE_SRGB);
+}
+
+STBIRDEF int stbir_resize_uint8_generic( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                               unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context)
+{
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, STBIR_TYPE_UINT8, filter, filter,
+        edge_wrap_mode, edge_wrap_mode, space);
+}
+
+STBIRDEF int stbir_resize_uint16_generic(const stbir_uint16 *input_pixels  , int input_w , int input_h , int input_stride_in_bytes,
+                                               stbir_uint16 *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context)
+{
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, STBIR_TYPE_UINT16, filter, filter,
+        edge_wrap_mode, edge_wrap_mode, space);
+}
+
+
+STBIRDEF int stbir_resize_float_generic( const float *input_pixels         , int input_w , int input_h , int input_stride_in_bytes,
+                                               float *output_pixels        , int output_w, int output_h, int output_stride_in_bytes,
+                                         int num_channels, int alpha_channel, int flags,
+                                         stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
+                                         void *alloc_context)
+{
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, STBIR_TYPE_FLOAT, filter, filter,
+        edge_wrap_mode, edge_wrap_mode, space);
+}
+
+
+STBIRDEF int stbir_resize(         const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context)
+{
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,NULL,num_channels,alpha_channel,flags, datatype, filter_horizontal, filter_vertical,
+        edge_mode_horizontal, edge_mode_vertical, space);
+}
+
+
+STBIRDEF int stbir_resize_subpixel(const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context,
+                                   float x_scale, float y_scale,
+                                   float x_offset, float y_offset)
+{
+    float transform[4];
+    transform[0] = x_scale;
+    transform[1] = y_scale;
+    transform[2] = x_offset;
+    transform[3] = y_offset;
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        0,0,1,1,transform,num_channels,alpha_channel,flags, datatype, filter_horizontal, filter_vertical,
+        edge_mode_horizontal, edge_mode_vertical, space);
+}
+
+STBIRDEF int stbir_resize_region(  const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
+                                         void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
+                                   stbir_datatype datatype,
+                                   int num_channels, int alpha_channel, int flags,
+                                   stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
+                                   stbir_filter filter_horizontal,  stbir_filter filter_vertical,
+                                   stbir_colorspace space, void *alloc_context,
+                                   float s0, float t0, float s1, float t1)
+{
+    return stbir__resize_arbitrary(alloc_context, input_pixels, input_w, input_h, input_stride_in_bytes,
+        output_pixels, output_w, output_h, output_stride_in_bytes,
+        s0,t0,s1,t1,NULL,num_channels,alpha_channel,flags, datatype, filter_horizontal, filter_vertical,
+        edge_mode_horizontal, edge_mode_vertical, space);
+}
+
+#endif // STB_IMAGE_RESIZE_IMPLEMENTATION
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/

src/tzozen.h

@@ -1,7 +1,7 @@
 #ifndef TZOZEN_H_
 #define TZOZEN_H_
 
-// TODO: https://github.com/nothings/stb/blob/master/docs/stb_howto.txt
+// todo: https://github.com/nothings/stb/blob/master/docs/stb_howto.txt
 //   [+] 1. #define LIBRARYNAME_IMPLEMENTATION
 //   [+] 2. AVOID DEPENDENCIES
 //   [+] 3. AVOID MALLOC
@@ -110,7 +110,7 @@ TZOZENDEF void json_object_push(Memory *memory, Json_Object *object, String key,
 TZOZENDEF Json_Value json_object_value_by_key(Json_Object object, String key);
 
 typedef struct {
-    // TODO(#26): because of the use of String-s Json_Number can hold an incorrect value
+    // todo(#26): because of the use of String-s Json_Number can hold an incorrect value
     //   But you can only get an incorrect Json_Number if you construct it yourself.
     //   Anything coming from parse_json_value should be always a correct number.
     String integer;
@@ -189,7 +189,7 @@ TZOZENDEF void print_json_value(FILE *stream, Json_Value value);
 #endif  // TZOZEN_H_
 
 #ifdef TZOZEN_IMPLEMENTATION
-// TODO: port https://github.com/tsoding/skedudle/pull/74 when it's merged
+// todo: port https://github.com/tsoding/skedudle/pull/74 when it's merged
 
 TZOZENDEF void *memory_alloc(Memory *memory, size_t size)
 {
@@ -550,7 +550,7 @@ TZOZENDEF Json_Result parse_json_number(Memory *memory, String source)
         chop(&source, 1);
     }
 
-    // TODO(#34): empty integer with fraction is not taken into account
+    // todo(#34): empty integer with fraction is not taken into account
     if (integer.len == 0
         || string_equal(integer, SLT("-"))
         || (integer.len > 1 && *integer.data == '0')
@@ -716,7 +716,7 @@ TZOZENDEF Json_Result parse_escape_sequence(Memory *memory, String source)
             // `parse_escape_sequence()` is used 2020-05-05) we are
             // copying it to `memory`.
             //
-            // TODO: We don't have any policy on what kind of memory we should always refer to int Json_Value-s and Json_Result-s
+            // todo: We don't have any policy on what kind of memory we should always refer to int Json_Value-s and Json_Result-s
             String s = {1, &unescape_map[i][1]};
             return result_success(drop(source, 1), json_string(s));
         }
@@ -813,7 +813,7 @@ TZOZENDEF Json_Result parse_json_string(Memory *memory, String source)
 
             source = result.rest;
         } else {
-            // TODO(#37): json parser is not aware of the input encoding
+            // todo(#37): json parser is not aware of the input encoding
             assert(buffer_size < buffer_capacity);
             buffer[buffer_size++] = *source.data;
             chop(&source, 1);
@@ -960,7 +960,7 @@ TZOZENDEF Json_Result parse_json_value_with_depth(Memory *memory, String source,
     return parse_json_number(memory, source);
 }
 
-// TODO(#40): parse_json_value is not aware of input encoding
+// todo(#40): parse_json_value is not aware of input encoding
 TZOZENDEF Json_Result parse_json_value(Memory *memory, String source)
 {
     return parse_json_value_with_depth(memory, source, 0);

src/vodus.cpp

@@ -11,6 +11,8 @@
 #include <gif_lib.h>
 #define STB_IMAGE_IMPLEMENTATION
 #include "./stb_image.h"
+#define STB_IMAGE_RESIZE_IMPLEMENTATION
+#include "./stb_image_resize.h"
 
 extern "C" {
 #include <libavcodec/avcodec.h>
@@ -21,6 +23,9 @@ extern "C" {
 #include "./aids.hpp"
 using namespace aids;
 
+#include <tmmintrin.h>
+#include <smmintrin.h>
+
 const size_t VODUS_MESSAGES_CAPACITY = 1024;
 
 // PLEASE READ THIS --> https://en.wikipedia.org/wiki/Single_Compilation_Unit

src/vodus_emotes.cpp

@@ -1,64 +1,41 @@
 struct Gif_Animat
 {
     String_View file_path;
-    GifFileType *file;
+    Animat32 animat;
     size_t index;
-    GraphicsControlBlock gcb;
     float delay_time;
 
     bool is_null() const
     {
-        return file == nullptr;
+        return animat.count == 0;
     }
 
     void update(float dt)
     {
-        if (is_null()) return;
-
-        delay_time -= dt * 100;
-        while (delay_time <= 0.0f) {
-            index = (index + 1) % file->ImageCount;
-            int ok = DGifSavedExtensionToGCB(file, index, &gcb);
-            if (!ok) {
-                println(stderr, "[ERROR] Could not retrieve Graphics Control Block from `", file_path, "`");
-                abort();
+        if (!is_null()) {
+            delay_time -= dt * 100;
+            while (delay_time <= 0.0f) {
+                index = (index + 1) % animat.count;
+                delay_time = animat.frame_delays[index] + delay_time;
             }
-            delay_time = gcb.DelayTime + delay_time;
         }
     }
 
     void slap_onto_image32(Image32 surface, int x, int y)
     {
-        if (is_null()) return;
-
-        slap_savedimage_onto_image32(
-                surface,
-                &file->SavedImages[index],
-                file->SColorMap,
-                gcb,
-                x, y);
-    }
-
-    void slap_onto_image32(Image32 surface, int x, int y, int w, int h)
-    {
-        if (is_null()) return;
-        slap_savedimage_onto_image32(
-                surface,
-                &file->SavedImages[index],
-                file->SColorMap,
-                gcb,
-                x, y,
-                w, h);
+        if (!is_null()) {
+            slap_image32_onto_image32(surface, animat.frames[index], x, y);
+        }
     }
 
     int width() const
     {
-        return is_null() ? 0 : file->SavedImages[index].ImageDesc.Width;
+        return is_null() ? 0 : animat.frames[index].width;
     }
 
     int height() const
     {
-        return is_null() ? 0 : file->SavedImages[index].ImageDesc.Height;
+        return is_null() ? 0 : animat.frames[index].height;
     }
 };
 
@@ -98,15 +75,15 @@ struct Emote
         return 0;
     }
 
-    void slap_onto_image32(Image32 surface, int x, int y, int w, int h)
+    void slap_onto_image32(Image32 surface, int x, int y)
     {
         switch (type) {
         case Png: {
-            slap_image32_onto_image32(surface, png, x, y, w, h);
+            slap_image32_onto_image32(surface, png, x, y);
         } return;
 
         case Gif: {
-            gif.slap_onto_image32(surface, x, y, w, h);
+            gif.slap_onto_image32(surface, x, y);
         } return;
         }
         assert(!"Incorrect Emote_Type value");
@@ -127,13 +104,14 @@ String_View file_extension(String_View filename)
 
 const char *string_view_as_cstr(String_View sv)
 {
-    char *cstr = (char *) malloc(sv.count);
+    char *cstr = (char *) malloc(sv.count + 1);
     if (!cstr) return cstr;
     memcpy(cstr, sv.data, sv.count);
+    cstr[sv.count] = '\0';
     return cstr;
 }
 
-Emote load_gif_emote(String_View file_path)
+Emote load_gif_emote(String_View file_path, size_t size)
 {
     Emote emote = {Emote::Gif};
 
@@ -141,27 +119,21 @@ Emote load_gif_emote(String_View file_path)
     assert(file_path_cstr);
     defer(free((void*) file_path_cstr));
 
-    int error = 0;
+    emote.gif.animat = load_animat32_from_gif(file_path_cstr, size);
     emote.gif.file_path = file_path;
-    emote.gif.file = DGifOpenFileName(file_path_cstr, &error);
-    if (error) {
-        println(stderr, "Could not read gif file: ", file_path);
-        exit(1);
-    }
-    assert(error == 0);
-    DGifSlurp(emote.gif.file);
 
     return emote;
 }
 
-Emote load_png_emote(String_View filepath)
+Emote load_png_emote(String_View filepath, size_t size)
 {
     Emote emote = {Emote::Png};
     auto filepath_cstr = string_view_as_cstr(filepath);
+
     assert(filepath_cstr);
     defer(free((void*) filepath_cstr));
 
-    emote.png = load_image32_from_png(filepath_cstr);
+    emote.png = load_image32_from_png(filepath_cstr, size);
     return emote;
 }
 
@@ -205,7 +177,7 @@ struct Emote_Cache
         }
     }
 
-    void populate_from_file(const char *mapping_filepath)
+    void populate_from_file(const char *mapping_filepath, size_t size)
     {
         auto mapping_csv = read_file_as_string_view(mapping_filepath);
         if (!mapping_csv.has_value) {
@@ -225,10 +197,10 @@ struct Emote_Cache
             }
 
             if (ext == "gif"_sv) {
-                emote_mapping[i].emote = load_gif_emote(filename);
+                emote_mapping[i].emote = load_gif_emote(filename, size);
                 gifs[gifs_count++] = &emote_mapping[i].emote.gif;
             } else if (ext == "png"_sv) {
-                emote_mapping[i].emote = load_png_emote(filename);
+                emote_mapping[i].emote = load_png_emote(filename, size);
             } else {
                 println(stderr, filename, " has unsupported extension ", ext);
                 abort();

src/vodus_image32.cpp

@@ -33,20 +33,99 @@ struct Image32
     }
 };
 
-Pixel32 mix_pixels(Pixel32 b32, Pixel32 a32)
+struct Animat32
 {
-    const float a32_alpha = a32.a / 255.0;
-    const float b32_alpha = b32.a / 255.0;
-    const float r_alpha = a32_alpha + b32_alpha * (1.0f - a32_alpha);
+    Image32 *frames;
+    int *frame_delays;
+    size_t count;
+};
+
+// NOTE: Stolen from https://stackoverflow.com/a/53707227
+void mix_pixels_sse(Pixel32 *src, Pixel32 *dst, Pixel32 *c)
+{
+    const __m128i _swap_mask =
+        _mm_set_epi8(7,  6,   5,  4,
+                     3,  2,   1,  0,
+                     15, 14, 13, 12,
+                     11, 10,  9,  8
+            );
+
+    const __m128i _aa =
+        _mm_set_epi8( 15,15,15,15,
+                      11,11,11,11,
+                      7,7,7,7,
+                      3,3,3,3 );
+
+    const __m128i _mask1 = _mm_set_epi16(-1,0,0,0, -1,0,0,0);
+    const __m128i _mask2 = _mm_set_epi16(0,-1,-1,-1, 0,-1,-1,-1);
+    const __m128i _v1 = _mm_set1_epi16( 1 );
+
+    __m128i _src = _mm_loadu_si128((__m128i*)src);
+    __m128i _src_a = _mm_shuffle_epi8(_src, _aa);
+
+    __m128i _dst = _mm_loadu_si128((__m128i*)dst);
+    __m128i _dst_a = _mm_shuffle_epi8(_dst, _aa);
+    __m128i _one_minus_src_a = _mm_subs_epu8(
+        _mm_set1_epi8(-1), _src_a);
+
+    __m128i _out = {};
+    {
+        __m128i _s_a = _mm_cvtepu8_epi16( _src_a );
+        __m128i _s = _mm_cvtepu8_epi16( _src );
+        __m128i _d = _mm_cvtepu8_epi16( _dst );
+        __m128i _d_a = _mm_cvtepu8_epi16( _one_minus_src_a );
+        _out = _mm_adds_epu16(
+            _mm_mullo_epi16(_s, _s_a),
+            _mm_mullo_epi16(_d, _d_a));
+        _out = _mm_srli_epi16(
+            _mm_adds_epu16(
+                _mm_adds_epu16( _v1, _out ),
+                _mm_srli_epi16( _out, 8 ) ), 8 );
+        _out = _mm_or_si128(
+            _mm_and_si128(_out,_mask2),
+            _mm_and_si128(
+                _mm_adds_epu16(
+                    _s_a,
+                    _mm_cvtepu8_epi16(_dst_a)), _mask1));
+    }
+
+    // compute _out2 using high quadword of of the _src and _dst
+    //...
+    __m128i _out2 = {};
+    {
+        __m128i _s_a = _mm_cvtepu8_epi16(_mm_shuffle_epi8(_src_a, _swap_mask));
+        __m128i _s = _mm_cvtepu8_epi16(_mm_shuffle_epi8(_src, _swap_mask));
+        __m128i _d = _mm_cvtepu8_epi16(_mm_shuffle_epi8(_dst, _swap_mask));
+        __m128i _d_a = _mm_cvtepu8_epi16(_mm_shuffle_epi8(_one_minus_src_a, _swap_mask));
+        _out2 = _mm_adds_epu16(
+            _mm_mullo_epi16(_s, _s_a),
+            _mm_mullo_epi16(_d, _d_a));
+        _out2 = _mm_srli_epi16(
+            _mm_adds_epu16(
+                _mm_adds_epu16( _v1, _out2 ),
+                _mm_srli_epi16( _out2, 8 ) ), 8 );
+        _out2 = _mm_or_si128(
+            _mm_and_si128(_out2,_mask2),
+            _mm_and_si128(
+                _mm_adds_epu16(
+                    _s_a,
+                    _mm_cvtepu8_epi16(_dst_a)), _mask1));
+    }
 
-    Pixel32 r = {};
+    __m128i _ret = _mm_packus_epi16( _out, _out2 );
 
-    r.r = (uint8_t) ((a32.r * a32_alpha + b32.r * b32_alpha * (1.0f - a32_alpha)) / r_alpha);
-    r.g = (uint8_t) ((a32.g * a32_alpha + b32.g * b32_alpha * (1.0f - a32_alpha)) / r_alpha);
-    r.b = (uint8_t) ((a32.b * a32_alpha + b32.b * b32_alpha * (1.0f - a32_alpha)) / r_alpha);
-    r.a = (uint8_t) (r_alpha * 255.0);
+    _mm_storeu_si128( (__m128i_u*) c, _ret );
+}
 
-    return r;
+Pixel32 mix_pixels(Pixel32 dst, Pixel32 src)
+{
+    uint8_t rev_src_a = 255 - src.a;
+    Pixel32 result;
+    result.r = ((uint16_t) src.r * (uint16_t) src.a + (uint16_t) dst.r * rev_src_a) >> 8;
+    result.g = ((uint16_t) src.g * (uint16_t) src.a + (uint16_t) dst.g * rev_src_a) >> 8;
+    result.b = ((uint16_t) src.b * (uint16_t) src.a + (uint16_t) dst.b * rev_src_a) >> 8;
+    result.a = dst.a;
+    return result;
 }
 
 void fill_image32_with_color(Image32 image, Pixel32 color)
@@ -78,32 +157,45 @@ void slap_ftbitmap_onto_image32(Image32 dest, FT_Bitmap *src, Pixel32 color, int
 }
 
 // TODO(#24): resizing version of slap_image32_onto_image32 requires some sort of interpolation
-void slap_image32_onto_image32(Image32 dest, Image32 src,
-                               int x, int y,
-                               size_t target_width,
-                               size_t target_height)
+void slap_image32_onto_image32(Image32 dst, Image32 src,
+                               int x0, int y0)
 {
-    for (size_t row = 0; (row < target_height); ++row) {
-        if (row + y < dest.height) {
-            for (size_t col = 0; (col < target_width); ++col) {
-                if (col + x < dest.width) {
-                    const int src_row = floorf((float) row / target_height * src.height);
-                    const int src_col = floorf((float) col / target_width * src.width);
-                    const auto dest_pixel = dest.pixels[(row + y) * dest.width + col + x];
-                    const auto src_pixel = src.pixels[src_row * src.width + src_col];
-                    dest.pixels[(row + y) * dest.width + col + x] =
-                        mix_pixels(dest_pixel, src_pixel);
-                }
-            }
+    const size_t SIMD_PIXEL_PACK_SIZE = 4;
+
+    size_t x1 = std::min(x0 + src.width, dst.width);
+    size_t y1 = std::min(y0 + src.height, dst.height);
+
+    for (size_t y = y0; y < y1; ++y) {
+        for (size_t x = x0; x < x1; x += SIMD_PIXEL_PACK_SIZE) {
+            assert(x >= 0);
+            assert(y >= 0);
+            assert(x < dst.width);
+            assert(y < dst.height);
+
+            assert(x - x0 >= 0);
+            assert(y - y0 >= 0);
+            assert(x - x0 < src.width);
+            assert(y - y0 < src.height);
+
+            // TODO(#90): SSE is not disablable
+            // TODO(#91): SSE rendering is slightly different from non SSE version
+            mix_pixels_sse(
+                &src.pixels[(y - y0) * src.width + (x - x0)],
+                &dst.pixels[y * dst.width + x],
+                &dst.pixels[y * dst.width + x]);
+
+            // dst.pixels[y * dst.width + x] =
+            //     mix_pixels(
+            //         dst.pixels[y * dst.width + x],
+            //         src.pixels[(y - y0) * src.width + (x - x0)]);
         }
     }
 }
 
-void slap_savedimage_onto_image32(Image32 dest,
-                                  SavedImage *src,
-                                  ColorMapObject *SColorMap,
-                                  GraphicsControlBlock gcb,
-                                  int x, int y)
+Image32 load_image32_from_savedimage(SavedImage *src,
+                                     ColorMapObject *SColorMap,
+                                     GraphicsControlBlock gcb,
+                                     size_t size)
 {
     assert(SColorMap);
     assert(SColorMap->BitsPerPixel <= 8);
@@ -112,64 +204,111 @@ void slap_savedimage_onto_image32(Image32 dest,
     assert(src->ImageDesc.Left == 0);
     assert(src->ImageDesc.Top == 0);
 
-    for (size_t row = 0; ((int) row < src->ImageDesc.Height); ++row) {
-        if (row + y < dest.height) {
-            for (size_t col = 0; ((int) col < src->ImageDesc.Width); ++col) {
-                if (col + x < dest.width) {
-                    auto index = src->RasterBits[row * src->ImageDesc.Width + col];
-                    if (index != gcb.TransparentColor) {
-                        auto pixel = SColorMap->Colors[index];
-                        dest.pixels[(row + y) * dest.width + col + x].r = pixel.Red;
-                        dest.pixels[(row + y) * dest.width + col + x].g = pixel.Green;
-                        dest.pixels[(row + y) * dest.width + col + x].b = pixel.Blue;
-                    }
-                }
+    Image32 origin = {};
+    origin.width = src->ImageDesc.Width;
+    origin.height = src->ImageDesc.Height;
+    origin.pixels = new Pixel32[origin.width * origin.height];
+    defer(delete[] origin.pixels);
+
+    for (size_t y = 0; y < origin.height; ++y) {
+        for (size_t x = 0; x < origin.width; ++x) {
+            auto index = src->RasterBits[y * origin.width + x];
+            auto pixel = SColorMap->Colors[index];
+            if (index != gcb.TransparentColor) {
+                origin.pixels[y * origin.width + x].r = pixel.Red;
+                origin.pixels[y * origin.width + x].g = pixel.Green;
+                origin.pixels[y * origin.width + x].b = pixel.Blue;
+                origin.pixels[y * origin.width + x].a = 255;
+            } else {
+                origin.pixels[y * origin.width + x] = {};
             }
         }
     }
+
+    const float emote_ratio = (float) origin.width / (float) origin.height;
+    Image32 result = {};
+    result.height = (int) size;
+    result.width = (int) floorf(result.height * emote_ratio);
+    result.pixels = new Pixel32[result.width * result.height];
+
+    stbir_resize_uint8((unsigned char *) origin.pixels, origin.width, origin.height, 0,
+                       (unsigned char *) result.pixels, result.width, result.height, 0,
+                       4);
+
+    return result;
 }
 
-void slap_savedimage_onto_image32(Image32 dest,
-                                  SavedImage *src,
-                                  ColorMapObject *SColorMap,
-                                  GraphicsControlBlock gcb,
-                                  int x, int y,
-                                  int target_width, int target_height)
+Animat32 load_animat32_from_gif(const char *filepath, size_t size)
 {
-    assert(SColorMap);
-    assert(SColorMap->BitsPerPixel <= 8);
-    assert(!SColorMap->SortFlag);
-    assert(src);
-    assert(src->ImageDesc.Left == 0);
-    assert(src->ImageDesc.Top == 0);
+    int error = 0;
+    GifFileType *gif_file = DGifOpenFileName(filepath, &error);
+    if (error) {
+        println(stderr, "[ERROR] Could not open gif file: ", filepath);
+        abort();
+    }
 
-    for (size_t row = 0; ((int) row < target_height); ++row) {
-        if (row + y < dest.height) {
-            for (size_t col = 0; ((int) col < target_width); ++col) {
-                if (col + x < dest.width) {
-                    int src_row = floorf((float) row / target_height * src->ImageDesc.Height);
-                    int src_col = floorf((float) col / target_width * src->ImageDesc.Width);
-
-                    auto index = src->RasterBits[src_row * src->ImageDesc.Width + src_col];
-                    if (index != gcb.TransparentColor) {
-                        auto pixel = SColorMap->Colors[index];
-                        dest.pixels[(row + y) * dest.width + col + x].r = pixel.Red;
-                        dest.pixels[(row + y) * dest.width + col + x].g = pixel.Green;
-                        dest.pixels[(row + y) * dest.width + col + x].b = pixel.Blue;
-                    }
-                }
-            }
+    if (DGifSlurp(gif_file) == GIF_ERROR) {
+        println(stderr, "[ERROR] Could not read gif file: ", filepath);
+        abort();
+    }
+
+    GraphicsControlBlock gcb = {};
+
+    Animat32 result = {};
+    result.count = gif_file->ImageCount;
+    result.frames = new Image32[result.count];
+    result.frame_delays = new int[result.count];
+
+    for (size_t index = 0; index < result.count; ++index) {
+        int ok = DGifSavedExtensionToGCB(gif_file, index, &gcb);
+        if (!ok) {
+            println(stderr, "[ERROR] Could not retrieve Graphics Control Block from `",
+                    filepath, "` on index ", index);
+            abort();
+        }
+
+        result.frame_delays[index] = gcb.DelayTime;
+
+        // TODO(#93): load_animat32_from_gif does not work on some gifs
+        if (gif_file->SavedImages[index].ImageDesc.Left == 0 &&
+            gif_file->SavedImages[index].ImageDesc.Top == 0) {
+          result.frames[index] = load_image32_from_savedimage(
+              &gif_file->SavedImages[index],
+              gif_file->SColorMap,
+              gcb,
+              size);
+        } else {
+            // println(stderr, filepath);
         }
     }
+
+    DGifCloseFile(gif_file, &error);
+    if (error) {
+        println(stderr, "[ERROR] Could not close gif file: ", filepath);
+        abort();
+    }
+
+    return result;
 }
 
-Image32 load_image32_from_png(const char *filepath)
+Image32 load_image32_from_png(const char *filepath, size_t size)
 {
     Image32 result = {};
     int w, h, n;
-    result.pixels = (Pixel32*) stbi_load(filepath, &w, &h, &n, 4);
-    result.width = w;
-    result.height = h;
+
+    unsigned char *origin = stbi_load(filepath, &w, &h, &n, 4);
+    defer(stbi_image_free(origin));
+
+    const float emote_ratio = (float) w / (float) h;
+    result.height = (int) size;
+    result.width = (int) floorf(result.height * emote_ratio);
+    result.pixels = new Pixel32[result.width * result.height];
+
+    stbir_resize_uint8(origin, w, h, 0,
+                       (unsigned char *) result.pixels,
+                       result.width, result.height, 0,
+                       4);
+
     return result;
 }
 

src/vodus_main.cpp

@@ -108,19 +108,13 @@ void render_message(Image32 surface, FT_Face face,
         if (maybe_emote.has_value) {
             auto emote = maybe_emote.unwrap;
 
-            const float emote_ratio = (float) emote.width() / emote.height();
-            const int emote_height = params.font_size;
-            const int emote_width = floorf(emote_height * emote_ratio);
-
-            if (*x + emote_width >= (int)surface.width) {
+            if (*x + emote.width() >= (int)surface.width) {
                 *x = 0;
                 *y += params.font_size;
             }
 
-            emote.slap_onto_image32(surface,
-                                    *x, *y - emote_height,
-                                    emote_width, emote_height);
-            *x += emote_width;
+            emote.slap_onto_image32(surface, *x, *y - emote.height());
+            *x += emote.width();
         } else {
             slap_text_onto_image32_wrapped(surface,
                                            face,
@@ -626,8 +620,14 @@ int main(int argc, char *argv[])
 
     // TODO(#44): BTTV mapping is not auto populated from the BTTV API
     // TODO(#45): FFZ mapping is not auto populated from the FFZ API
+    // TODO(#92): loading emotes step is too slow
+    // Can we speed it up?
     Emote_Cache emote_cache = { };
-    emote_cache.populate_from_file("./mapping.csv");
+    {
+        clock_t begin = clock();
+        emote_cache.populate_from_file("./mapping.csv", params.font_size);
+        println(stdout, "Loading emotes took ", (float) (clock() - begin) / (float) CLOCKS_PER_SEC, " seconds");
+    }
 
     // FFMPEG INIT START //////////////////////////////
     AVCodec *codec = fail_if_null(
@@ -710,7 +710,11 @@ int main(int argc, char *argv[])
     encoder.packet = packet;
     encoder.output_stream = output_stream;
 
-    sample_chat_log_animation(face, &encoder, &emote_cache, params);
+    {
+        clock_t begin = clock();
+        sample_chat_log_animation(face, &encoder, &emote_cache, params);
+        println(stdout, "Rendering took ", (float) (clock() - begin) / (float) CLOCKS_PER_SEC, " seconds");
+    }
 
     encode_avframe(context, NULL, packet, output_stream);
 

third_party/build_third_party.sh

@@ -1,5 +1,6 @@
 #!/bin/sh
 
+# TODO(#89): Integrate ./build_third_party.sh into the main build process
 FFMPEG_VERSION=4.3
 GIFLIB_VERSION=5.2.1