Added support for loading and saving PNG images using stb_image

include/SDL3/SDL_surface.h

@@ -559,7 +559,7 @@ extern SDL_DECLSPEC SDL_Surface * SDLCALL SDL_LoadBMP(const char *file);
 extern SDL_DECLSPEC bool SDLCALL SDL_SaveBMP_IO(SDL_Surface *surface, SDL_IOStream *dst, bool closeio);
 
 /**
- * Save a surface to a file.
+ * Save a surface to a file in BMP format.
  *
  * Surfaces with a 24-bit, 32-bit and paletted 8-bit format get saved in the
  * BMP directly. Other RGB formats with 8-bit or higher get converted to a
@@ -581,6 +581,84 @@ extern SDL_DECLSPEC bool SDLCALL SDL_SaveBMP_IO(SDL_Surface *surface, SDL_IOStre
  */
 extern SDL_DECLSPEC bool SDLCALL SDL_SaveBMP(SDL_Surface *surface, const char *file);
 
+/**
+ * Load a PNG image from a seekable SDL data stream.
+ *
+ * The new surface should be freed with SDL_DestroySurface(). Not doing so
+ * will result in a memory leak.
+ *
+ * \param src the data stream for the surface.
+ * \param closeio if true, calls SDL_CloseIO() on `src` before returning, even
+ *                in the case of an error.
+ * \returns a pointer to a new SDL_Surface structure or NULL on failure; call
+ *          SDL_GetError() for more information.
+ *
+ * \threadsafety It is safe to call this function from any thread.
+ *
+ * \since This function is available since SDL 3.2.0.
+ *
+ * \sa SDL_DestroySurface
+ * \sa SDL_LoadPNG
+ * \sa SDL_SavePNG_IO
+ */
+extern SDL_DECLSPEC SDL_Surface * SDLCALL SDL_LoadPNG_IO(SDL_IOStream *src, bool closeio);
+
+/**
+ * Load a PNG image from a file.
+ *
+ * The new surface should be freed with SDL_DestroySurface(). Not doing so
+ * will result in a memory leak.
+ *
+ * \param file the PNG file to load.
+ * \returns a pointer to a new SDL_Surface structure or NULL on failure; call
+ *          SDL_GetError() for more information.
+ *
+ * \threadsafety It is safe to call this function from any thread.
+ *
+ * \since This function is available since SDL 3.2.0.
+ *
+ * \sa SDL_DestroySurface
+ * \sa SDL_LoadPNG_IO
+ * \sa SDL_SavePNG
+ */
+extern SDL_DECLSPEC SDL_Surface * SDLCALL SDL_LoadPNG(const char *file);
+
+/**
+ * Save a surface to a seekable SDL data stream in PNG format.
+ *
+ * \param surface the SDL_Surface structure containing the image to be saved.
+ * \param dst a data stream to save to.
+ * \param closeio if true, calls SDL_CloseIO() on `dst` before returning, even
+ *                in the case of an error.
+ * \returns true on success or false on failure; call SDL_GetError() for more
+ *          information.
+ *
+ * \threadsafety This function is not thread safe.
+ *
+ * \since This function is available since SDL 3.2.0.
+ *
+ * \sa SDL_LoadPNG_IO
+ * \sa SDL_SavePNG
+ */
+extern SDL_DECLSPEC bool SDLCALL SDL_SavePNG_IO(SDL_Surface *surface, SDL_IOStream *dst, bool closeio);
+
+/**
+ * Save a surface to a file in PNG format.
+ *
+ * \param surface the SDL_Surface structure containing the image to be saved.
+ * \param file a file to save to.
+ * \returns true on success or false on failure; call SDL_GetError() for more
+ *          information.
+ *
+ * \threadsafety This function is not thread safe.
+ *
+ * \since This function is available since SDL 3.2.0.
+ *
+ * \sa SDL_LoadPNG
+ * \sa SDL_SavePNG_IO
+ */
+extern SDL_DECLSPEC bool SDLCALL SDL_SavePNG(SDL_Surface *surface, const char *file);
+
 /**
  * Set the RLE acceleration hint for a surface.
  *

src/dynapi/SDL_dynapi.sym

@@ -1260,6 +1260,10 @@ SDL3_0.0.0 {
     SDL_SetTexturePalette;
     SDL_GetTexturePalette;
     SDL_GetGPURendererDevice;
+    SDL_LoadPNG_IO;
+    SDL_LoadPNG;
+    SDL_SavePNG_IO;
+    SDL_SavePNG;
     # extra symbols go here (don't modify this line)
   local: *;
 };

src/dynapi/SDL_dynapi_overrides.h

@@ -1286,3 +1286,7 @@
 #define SDL_SetTexturePalette SDL_SetTexturePalette_REAL
 #define SDL_GetTexturePalette SDL_GetTexturePalette_REAL
 #define SDL_GetGPURendererDevice SDL_GetGPURendererDevice_REAL
+#define SDL_LoadPNG_IO SDL_LoadPNG_IO_REAL
+#define SDL_LoadPNG SDL_LoadPNG_REAL
+#define SDL_SavePNG_IO SDL_SavePNG_IO_REAL
+#define SDL_SavePNG SDL_SavePNG_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -1294,3 +1294,7 @@ SDL_DYNAPI_PROC(Sint32,JNI_OnLoad,(JavaVM *a, void *b),(a,b),return)
 SDL_DYNAPI_PROC(bool,SDL_SetTexturePalette,(SDL_Texture *a,SDL_Palette *b),(a,b),return)
 SDL_DYNAPI_PROC(SDL_Palette*,SDL_GetTexturePalette,(SDL_Texture *a),(a),return)
 SDL_DYNAPI_PROC(SDL_GPUDevice*,SDL_GetGPURendererDevice,(SDL_Renderer *a),(a),return)
+SDL_DYNAPI_PROC(SDL_Surface*,SDL_LoadPNG_IO,(SDL_IOStream *a,bool b),(a,b),return)
+SDL_DYNAPI_PROC(SDL_Surface*,SDL_LoadPNG,(const char *a),(a),return)
+SDL_DYNAPI_PROC(bool,SDL_SavePNG_IO,(SDL_Surface *a,SDL_IOStream *b,bool c),(a,b,c),return)
+SDL_DYNAPI_PROC(bool,SDL_SavePNG,(SDL_Surface *a,const char *b),(a,b),return)

src/video/SDL_stb.c

@@ -48,12 +48,11 @@
 #if defined(SDL_NEON_INTRINSICS)
 #define STBI_NEON
 #endif
+#define STBI_ONLY_PNG
 #define STBI_ONLY_JPEG
 #define STBI_NO_GIF
-#define STBI_NO_PNG
 #define STBI_NO_HDR
 #define STBI_NO_LINEAR
-#define STBI_NO_ZLIB
 #define STBI_NO_STDIO
 #define STBI_ASSERT SDL_assert
 #define STB_IMAGE_IMPLEMENTATION
@@ -127,6 +126,252 @@ bool SDL_ConvertPixels_STB(int width, int height,
 #endif
 }
 
+#ifdef SDL_HAVE_STB
+static int IMG_LoadSTB_IO_read(void *user, char *data, int size)
+{
+    size_t amount = SDL_ReadIO((SDL_IOStream*)user, data, size);
+    return (int)amount;
+}
+
+static void IMG_LoadSTB_IO_skip(void *user, int n)
+{
+    SDL_SeekIO((SDL_IOStream*)user, n, SDL_IO_SEEK_CUR);
+}
+
+static int IMG_LoadSTB_IO_eof(void *user)
+{
+    SDL_IOStream *src = (SDL_IOStream*)user;
+    return SDL_GetIOStatus(src) == SDL_IO_STATUS_EOF;
+}
+
+static SDL_Surface *SDL_LoadSTB_IO(SDL_IOStream *src)
+{
+    Sint64 start;
+    Uint8 magic[26];
+    int w, h, format;
+    stbi_uc *pixels;
+    stbi_io_callbacks rw_callbacks;
+    SDL_Surface *surface = NULL;
+    bool use_palette = false;
+    unsigned int palette_colors[256];
+
+    // src has already been validated
+    start = SDL_TellIO(src);
+
+    if (SDL_ReadIO(src, magic, sizeof(magic)) == sizeof(magic)) {
+        const Uint8 PNG_COLOR_INDEXED = 3;
+        if (magic[0] == 0x89 &&
+            magic[1] == 'P' &&
+            magic[2] == 'N' &&
+            magic[3] == 'G' &&
+            magic[12] == 'I' &&
+            magic[13] == 'H' &&
+            magic[14] == 'D' &&
+            magic[15] == 'R' &&
+            magic[25] == PNG_COLOR_INDEXED) {
+            use_palette = true;
+        }
+    }
+    SDL_SeekIO(src, start, SDL_IO_SEEK_SET);
+
+    /* Load the image data */
+    rw_callbacks.read = IMG_LoadSTB_IO_read;
+    rw_callbacks.skip = IMG_LoadSTB_IO_skip;
+    rw_callbacks.eof = IMG_LoadSTB_IO_eof;
+    w = h = format = 0; /* silence warning */
+    if (use_palette) {
+        /* Unused palette entries will be opaque white */
+        SDL_memset(palette_colors, 0xff, sizeof(palette_colors));
+
+        pixels = stbi_load_from_callbacks_with_palette(
+            &rw_callbacks,
+            src,
+            &w,
+            &h,
+            palette_colors,
+            SDL_arraysize(palette_colors)
+        );
+    } else {
+        pixels = stbi_load_from_callbacks(
+            &rw_callbacks,
+            src,
+            &w,
+            &h,
+            &format,
+            STBI_default
+        );
+    }
+    if (!pixels) {
+        SDL_SeekIO(src, start, SDL_IO_SEEK_SET);
+        return NULL;
+    }
+
+    if (use_palette) {
+        surface = SDL_CreateSurfaceFrom(
+            w,
+            h,
+            SDL_PIXELFORMAT_INDEX8,
+            pixels,
+            w
+        );
+        if (surface) {
+            bool has_colorkey = false;
+            int colorkey_index = -1;
+            bool has_alpha = false;
+            SDL_Palette *palette = SDL_CreateSurfacePalette(surface);
+            if (palette) {
+                int i;
+                Uint8 *palette_bytes = (Uint8 *)palette_colors;
+
+                for (i = 0; i < palette->ncolors; i++) {
+                    palette->colors[i].r = *palette_bytes++;
+                    palette->colors[i].g = *palette_bytes++;
+                    palette->colors[i].b = *palette_bytes++;
+                    palette->colors[i].a = *palette_bytes++;
+                    if (palette->colors[i].a != SDL_ALPHA_OPAQUE) {
+                        if (palette->colors[i].a == SDL_ALPHA_TRANSPARENT && !has_colorkey) {
+                            has_colorkey = true;
+                            colorkey_index = i;
+                        } else {
+                            /* Partial opacity or multiple colorkeys */
+                            has_alpha = true;
+                        }
+                    }
+                }
+            }
+            if (has_alpha) {
+                SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_BLEND);
+            } else if (has_colorkey) {
+                SDL_SetSurfaceColorKey(surface, true, colorkey_index);
+            }
+
+            /* FIXME: This sucks. It'd be better to allocate the surface first, then
+             * write directly to the pixel buffer:
+             * https://github.com/nothings/stb/issues/58
+             * -flibit
+             */
+            surface->flags &= ~SDL_SURFACE_PREALLOCATED;
+        }
+
+    } else if (format == STBI_grey || format == STBI_rgb || format == STBI_rgb_alpha) {
+        surface = SDL_CreateSurfaceFrom(
+            w,
+            h,
+            (format == STBI_rgb_alpha) ? SDL_PIXELFORMAT_RGBA32 :
+            (format == STBI_rgb) ? SDL_PIXELFORMAT_RGB24 :
+            SDL_PIXELFORMAT_INDEX8,
+            pixels,
+            w * format
+        );
+        if (surface) {
+            /* Set a grayscale palette for gray images */
+            if (surface->format == SDL_PIXELFORMAT_INDEX8) {
+                SDL_Palette *palette = SDL_CreateSurfacePalette(surface);
+                if (palette) {
+                    int i;
+
+                    for (i = 0; i < palette->ncolors; i++) {
+                        palette->colors[i].r = (Uint8)i;
+                        palette->colors[i].g = (Uint8)i;
+                        palette->colors[i].b = (Uint8)i;
+                    }
+                }
+            }
+
+            /* FIXME: This sucks. It'd be better to allocate the surface first, then
+             * write directly to the pixel buffer:
+             * https://github.com/nothings/stb/issues/58
+             * -flibit
+             */
+            surface->flags &= ~SDL_SURFACE_PREALLOCATED;
+        }
+
+    } else if (format == STBI_grey_alpha) {
+        surface = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_RGBA32);
+        if (surface) {
+            Uint8 *src_ptr = pixels;
+            Uint8 *dst = (Uint8 *)surface->pixels;
+            int skip = surface->pitch - (surface->w * 4);
+            int row, col;
+
+            for (row = 0; row < h; ++row) {
+                for (col = 0; col < w; ++col) {
+                    Uint8 c = *src_ptr++;
+                    Uint8 a = *src_ptr++;
+                    *dst++ = c;
+                    *dst++ = c;
+                    *dst++ = c;
+                    *dst++ = a;
+                }
+                dst += skip;
+            }
+            stbi_image_free(pixels);
+        }
+    } else {
+        SDL_SetError("Unknown image format: %d", format);
+    }
+
+    if (!surface) {
+        /* The error message should already be set */
+        stbi_image_free(pixels); /* calls SDL_free() */
+        SDL_SeekIO(src, start, SDL_IO_SEEK_SET);
+    }
+    return surface;
+}
+#endif // SDL_HAVE_STB
+
+SDL_Surface *SDL_LoadPNG_IO(SDL_IOStream *src, bool closeio)
+{
+    Sint64 start;
+    Uint8 magic[4];
+    bool is_PNG;
+    SDL_Surface *surface = NULL;
+
+    CHECK_PARAM(!src) {
+        SDL_InvalidParamError("src");
+        goto done;
+    }
+
+    start = SDL_TellIO(src);
+    is_PNG = false;
+    if (SDL_ReadIO(src, magic, sizeof(magic)) == sizeof(magic)) {
+        if (magic[0] == 0x89 &&
+            magic[1] == 'P' &&
+            magic[2] == 'N' &&
+            magic[3] == 'G') {
+            is_PNG = true;
+        }
+    }
+    SDL_SeekIO(src, start, SDL_IO_SEEK_SET);
+
+    if (!is_PNG) {
+        SDL_SetError("File is not a PNG file");
+        goto done;
+    }
+
+#ifdef SDL_HAVE_STB
+    surface = SDL_LoadSTB_IO(src);
+#else
+    SDL_SetError("SDL not built with STB image support");
+#endif // SDL_HAVE_STB
+
+done:
+    if (src && closeio) {
+        SDL_CloseIO(src);
+    }
+    return surface;
+}
+
+SDL_Surface *SDL_LoadPNG(const char *file)
+{
+    SDL_IOStream *stream = SDL_IOFromFile(file, "rb");
+    if (!stream) {
+        return NULL;
+    }
+
+    return SDL_LoadPNG_IO(stream, true);
+}
+
 #ifdef SDL_HAVE_STB
 static void SDL_STBWriteFunc(void *context, void *data, int size)
 {
@@ -136,46 +381,46 @@ static void SDL_STBWriteFunc(void *context, void *data, int size)
 
 bool SDL_SavePNG_IO(SDL_Surface *surface, SDL_IOStream *dst, bool closeio)
 {
-#ifdef SDL_HAVE_STB
-    bool retval = true;
+    bool retval = false;
 
     // Make sure we have somewhere to save
     CHECK_PARAM(!SDL_SurfaceValid(surface)) {
-        retval = SDL_InvalidParamError("surface");
+        SDL_InvalidParamError("surface");
         goto done;
     }
     CHECK_PARAM(!dst) {
-        retval = SDL_InvalidParamError("dst");
+        SDL_InvalidParamError("dst");
         goto done;
     }
 
+#ifdef SDL_HAVE_STB
     bool free_surface = false;
-    if (surface->format != SDL_PIXELFORMAT_ABGR8888) {
-        surface = SDL_ConvertSurface(surface, SDL_PIXELFORMAT_ABGR8888);
+    if (surface->format != SDL_PIXELFORMAT_RGBA32) {
+        surface = SDL_ConvertSurface(surface, SDL_PIXELFORMAT_RGBA32);
         if (!surface) {
-            retval = false;
             goto done;
         }
         free_surface = true;
     }
 
-    if (!stbi_write_png_to_func(SDL_STBWriteFunc, dst, surface->w, surface->h, 4, surface->pixels, surface->pitch)) {
-        retval = SDL_SetError("Failed to write PNG");
+    if (stbi_write_png_to_func(SDL_STBWriteFunc, dst, surface->w, surface->h, 4, surface->pixels, surface->pitch)) {
+        retval = true;
+    } else {
+        SDL_SetError("Failed to write PNG");
     }
 
     if (free_surface) {
         SDL_DestroySurface(surface);
     }
+#else
+    SDL_SetError("SDL not built with STB image support");
+#endif
 
 done:
     if (dst && closeio) {
-        retval = SDL_CloseIO(dst);
+        retval &= SDL_CloseIO(dst);
     }
-
     return retval;
-#else
-    return SDL_SetError("SDL not built with STB image write support");
-#endif
 }
 
 bool SDL_SavePNG(SDL_Surface *surface, const char *file)
@@ -188,6 +433,6 @@ bool SDL_SavePNG(SDL_Surface *surface, const char *file)
 
     return SDL_SavePNG_IO(surface, stream, true);
 #else
-    return SDL_SetError("SDL not built with STB image write support");
+    return SDL_SetError("SDL not built with STB image support");
 #endif
 }

src/video/SDL_stb_c.h

@@ -27,7 +27,5 @@
 // Image conversion functions
 
 extern bool SDL_ConvertPixels_STB(int width, int height, SDL_PixelFormat src_format, SDL_Colorspace src_colorspace, SDL_PropertiesID src_properties, const void *src, int src_pitch, SDL_PixelFormat dst_format, SDL_Colorspace dst_colorspace, SDL_PropertiesID dst_properties, void *dst, int dst_pitch);
-extern bool SDL_SavePNG_IO(SDL_Surface *surface, SDL_IOStream *dst, bool closeio);
-extern bool SDL_SavePNG(SDL_Surface *surface, const char *file);
 
 #endif // SDL_stb_c_h_

src/video/stb_image.h

@@ -453,8 +453,8 @@ STBIDEF int stbi_convert_wchar_to_utf8(char *buffer, size_t bufferlen, const wch
 
 #if 0 /* not used in SDL */
 STBIDEF stbi_uc *stbi_load_from_memory_with_palette   (stbi_uc           const *buffer, int len , int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len);
-STBIDEF stbi_uc *stbi_load_from_callbacks_with_palette(stbi_io_callbacks const *clbk, void *user, int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len);
 #endif
+STBIDEF stbi_uc *stbi_load_from_callbacks_with_palette(stbi_io_callbacks const *clbk, void *user, int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len);
 
 ////////////////////////////////////
 //
@@ -559,14 +559,18 @@ STBIDEF void stbi_set_flip_vertically_on_load_thread(int flag_true_if_should_fli
 // ZLIB client - used by PNG, available for other purposes
 
 #ifndef STBI_NO_ZLIB
+#if 0 /* not used in SDL */
 STBIDEF char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen);
+#endif
 STBIDEF char *stbi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len, int initial_size, int *outlen, int parse_header);
+#if 0 /* not used in SDL */
 STBIDEF char *stbi_zlib_decode_malloc(const char *buffer, int len, int *outlen);
 STBIDEF int   stbi_zlib_decode_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);
 
 STBIDEF char *stbi_zlib_decode_noheader_malloc(const char *buffer, int len, int *outlen);
 STBIDEF int   stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);
 #endif
+#endif
 
 
 #ifdef __cplusplus
@@ -897,7 +901,6 @@ static void stbi__start_mem(stbi__context *s, stbi_uc const *buffer, int len)
    s->img_buffer_end = s->img_buffer_original_end = (stbi_uc *) buffer+len;
 }
 
-#if 0 /* not used in SDL */
 // initialize a callback-based context
 static void stbi__start_callbacks(stbi__context *s, stbi_io_callbacks *c, void *user)
 {
@@ -910,7 +913,6 @@ static void stbi__start_callbacks(stbi__context *s, stbi_io_callbacks *c, void *
    stbi__refill_buffer(s);
    s->img_buffer_original_end = s->img_buffer_end;
 }
-#endif
 
 #ifndef STBI_NO_STDIO
 
@@ -1353,7 +1355,6 @@ static void stbi__vertical_flip_slices(void *image, int w, int h, int z, int byt
 }
 #endif
 
-#if 0 /* not used in SDL */
 static unsigned char *stbi__load_indexed(stbi__context *s, int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len)
 {
    stbi__result_info ri;
@@ -1386,7 +1387,6 @@ static unsigned char *stbi__load_indexed(stbi__context *s, int *x, int *y, unsig
 
    return (unsigned char *) result;
 }
-#endif /**/
 
 static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x, int *y, int *comp, int req_comp)
 {
@@ -1568,7 +1568,6 @@ STBIDEF stbi_uc *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, i
    return stbi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
 }
 
-#if 0 /* not used in SDL */
 STBIDEF stbi_uc *stbi_load_from_callbacks(stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
 {
    stbi__context s;
@@ -1576,12 +1575,14 @@ STBIDEF stbi_uc *stbi_load_from_callbacks(stbi_io_callbacks const *clbk, void *u
    return stbi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
 }
 
+#if 0 /* not used in SDL */
 STBIDEF stbi_uc *stbi_load_from_memory_with_palette(stbi_uc const *buffer, int len, int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len)
 {
     stbi__context s;
     stbi__start_mem(&s, buffer, len);
     return stbi__load_indexed(&s, x, y, palette_buffer, palette_buffer_len);
 }
+#endif
 
 STBIDEF stbi_uc *stbi_load_from_callbacks_with_palette(stbi_io_callbacks const *clbk, void *user, int *x, int *y, unsigned int *palette_buffer, int palette_buffer_len)
 {
@@ -1589,7 +1590,6 @@ STBIDEF stbi_uc *stbi_load_from_callbacks_with_palette(stbi_io_callbacks const *
     stbi__start_callbacks(&s, (stbi_io_callbacks *)clbk, user);
     return stbi__load_indexed(&s, x, y, palette_buffer, palette_buffer_len);
 }
-#endif
 
 #ifndef STBI_NO_GIF
 STBIDEF stbi_uc *stbi_load_gif_from_memory(stbi_uc const *buffer, int len, int **delays, int *x, int *y, int *z, int *comp, int req_comp)
@@ -4735,6 +4735,7 @@ static int stbi__do_zlib(stbi__zbuf *a, char *obuf, int olen, int exp, int parse
    return stbi__parse_zlib(a, parse_header);
 }
 
+#if 0 /* not used in SDL */
 STBIDEF char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen)
 {
    stbi__zbuf a;
@@ -4755,6 +4756,7 @@ STBIDEF char *stbi_zlib_decode_malloc(char const *buffer, int len, int *outlen)
 {
    return stbi_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
 }
+#endif /* */
 
 STBIDEF char *stbi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len, int initial_size, int *outlen, int parse_header)
 {
@@ -4772,6 +4774,7 @@ STBIDEF char *stbi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, i
    }
 }
 
+#if 0 /* not used in SDL */
 STBIDEF int stbi_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer, int ilen)
 {
    stbi__zbuf a;
@@ -4809,6 +4812,7 @@ STBIDEF int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char
    else
       return -1;
 }
+#endif /* */
 #endif
 
 // public domain "baseline" PNG decoder   v0.10  Sean Barrett 2006-11-18

test/testsymbols.c

@@ -1335,6 +1335,10 @@ const static struct {
     SDL_SYMBOL_ITEM(SDL_SetTexturePalette),
     SDL_SYMBOL_ITEM(SDL_GetTexturePalette),
     SDL_SYMBOL_ITEM(SDL_GetGPURendererDevice),
+    SDL_SYMBOL_ITEM(SDL_LoadPNG_IO),
+    SDL_SYMBOL_ITEM(SDL_LoadPNG),
+    SDL_SYMBOL_ITEM(SDL_SavePNG_IO),
+    SDL_SYMBOL_ITEM(SDL_SavePNG),
     /* extra symbols go here (don't modify this line) */
     { NULL, NULL }
 };