refactor bmp header parser for sharing with stbi_info

stb_image.h

@@ -4598,19 +4598,22 @@ static int stbi__shiftsigned(int v, int shift, int bits)
    return result;
 }
 
-static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int req_comp)
+typedef struct
 {
-   stbi_uc *out;
-   unsigned int mr=0,mg=0,mb=0,ma=0, all_a=255;
-   stbi_uc pal[256][4];
-   int psize=0,i,j,compress=0,width;
-   int bpp, flip_vertically, pad, target, offset, hsz;
+   int bpp, offset, hsz;
+   unsigned int mr,mg,mb,ma, all_a;
+} stbi__bmp_data;
+
+static void *stbi__bmp_parse_header(stbi__context *s, stbi__bmp_data *info)
+{
+   int hsz;
    if (stbi__get8(s) != 'B' || stbi__get8(s) != 'M') return stbi__errpuc("not BMP", "Corrupt BMP");
    stbi__get32le(s); // discard filesize
    stbi__get16le(s); // discard reserved
    stbi__get16le(s); // discard reserved
-   offset = stbi__get32le(s);
-   hsz = stbi__get32le(s);
+   info->offset = stbi__get32le(s);
+   info->hsz = hsz = stbi__get32le(s);
+   
    if (hsz != 12 && hsz != 40 && hsz != 56 && hsz != 108 && hsz != 124) return stbi__errpuc("unknown BMP", "BMP type not supported: unknown");
    if (hsz == 12) {
       s->img_x = stbi__get16le(s);
@@ -4620,15 +4623,10 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
       s->img_y = stbi__get32le(s);
    }
    if (stbi__get16le(s) != 1) return stbi__errpuc("bad BMP", "bad BMP");
-   bpp = stbi__get16le(s);
-   if (bpp == 1) return stbi__errpuc("monochrome", "BMP type not supported: 1-bit");
-   flip_vertically = ((int) s->img_y) > 0;
-   s->img_y = abs((int) s->img_y);
-   if (hsz == 12) {
-      if (bpp < 24)
-         psize = (offset - 14 - 24) / 3;
-   } else {
-      compress = stbi__get32le(s);
+   info->bpp = stbi__get16le(s);
+   if (info->bpp == 1) return stbi__errpuc("monochrome", "BMP type not supported: 1-bit");
+   if (hsz != 12) {
+      int compress = stbi__get32le(s);
       if (compress == 1 || compress == 2) return stbi__errpuc("BMP RLE", "BMP type not supported: RLE");
       stbi__get32le(s); // discard sizeof
       stbi__get32le(s); // discard hres
@@ -4642,26 +4640,26 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
             stbi__get32le(s);
             stbi__get32le(s);
          }
-         if (bpp == 16 || bpp == 32) {
-            mr = mg = mb = 0;
+         if (info->bpp == 16 || info->bpp == 32) {
+            info->mr = info->mg = info->mb = 0;
             if (compress == 0) {
-               if (bpp == 32) {
-                  mr = 0xffu << 16;
-                  mg = 0xffu <<  8;
-                  mb = 0xffu <<  0;
-                  ma = 0xffu << 24;
-                  all_a = 0; // if all_a is 0 at end, then we loaded alpha channel but it was all 0
+               if (info->bpp == 32) {
+                  info->mr = 0xffu << 16;
+                  info->mg = 0xffu <<  8;
+                  info->mb = 0xffu <<  0;
+                  info->ma = 0xffu << 24;
+                  info->all_a = 0; // if all_a is 0 at end, then we loaded alpha channel but it was all 0
                } else {
-                  mr = 31u << 10;
-                  mg = 31u <<  5;
-                  mb = 31u <<  0;
+                  info->mr = 31u << 10;
+                  info->mg = 31u <<  5;
+                  info->mb = 31u <<  0;
                }
             } else if (compress == 3) {
-               mr = stbi__get32le(s);
-               mg = stbi__get32le(s);
-               mb = stbi__get32le(s);
+               info->mr = stbi__get32le(s);
+               info->mg = stbi__get32le(s);
+               info->mb = stbi__get32le(s);
                // not documented, but generated by photoshop and handled by mspaint
-               if (mr == mg && mg == mb) {
+               if (info->mr == info->mg && info->mg == info->mb) {
                   // ?!?!?
                   return stbi__errpuc("bad BMP", "bad BMP");
                }
@@ -4669,11 +4667,13 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
                return stbi__errpuc("bad BMP", "bad BMP");
          }
       } else {
-         STBI_ASSERT(hsz == 108 || hsz == 124);
-         mr = stbi__get32le(s);
-         mg = stbi__get32le(s);
-         mb = stbi__get32le(s);
-         ma = stbi__get32le(s);
+         int i;
+         if (hsz != 108 && hsz != 124)
+            return stbi__errpuc("bad BMP", "bad BMP");
+         info->mr = stbi__get32le(s);
+         info->mg = stbi__get32le(s);
+         info->mb = stbi__get32le(s);
+         info->ma = stbi__get32le(s);
          stbi__get32le(s); // discard color space
          for (i=0; i < 12; ++i)
             stbi__get32le(s); // discard color space parameters
@@ -4684,35 +4684,68 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
             stbi__get32le(s); // discard reserved
          }
       }
-      if (bpp < 16)
-         psize = (offset - 14 - hsz) >> 2;
    }
+   return (void *) 1;
+}
+
+
+static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int req_comp)
+{
+   stbi_uc *out;
+   unsigned int mr=0,mg=0,mb=0,ma=0, all_a;
+   stbi_uc pal[256][4];
+   int psize=0,i,j,width;
+   int flip_vertically, pad, target;
+   stbi__bmp_data info;
+
+   info.all_a = 255;   
+   if (stbi__bmp_parse_header(s, &info) == NULL)
+      return NULL; // error code already set
+
+   flip_vertically = ((int) s->img_y) > 0;
+   s->img_y = abs((int) s->img_y);
+
+   mr = info.mr;
+   mg = info.mg;
+   mb = info.mb;
+   ma = info.ma;
+   all_a = info.all_a;
+
+   if (info.hsz == 12) {
+      if (info.bpp < 24)
+         psize = (info.offset - 14 - 24) / 3;
+   } else {
+      if (info.bpp < 16)
+         psize = (info.offset - 14 - info.hsz) >> 2;
+   }
+
    s->img_n = ma ? 4 : 3;
    if (req_comp && req_comp >= 3) // we can directly decode 3 or 4
       target = req_comp;
    else
       target = s->img_n; // if they want monochrome, we'll post-convert
+
    out = (stbi_uc *) stbi__malloc(target * s->img_x * s->img_y);
    if (!out) return stbi__errpuc("outofmem", "Out of memory");
-   if (bpp < 16) {
+   if (info.bpp < 16) {
       int z=0;
       if (psize == 0 || psize > 256) { STBI_FREE(out); return stbi__errpuc("invalid", "Corrupt BMP"); }
       for (i=0; i < psize; ++i) {
          pal[i][2] = stbi__get8(s);
          pal[i][1] = stbi__get8(s);
          pal[i][0] = stbi__get8(s);
-         if (hsz != 12) stbi__get8(s);
+         if (info.hsz != 12) stbi__get8(s);
          pal[i][3] = 255;
       }
-      stbi__skip(s, offset - 14 - hsz - psize * (hsz == 12 ? 3 : 4));
-      if (bpp == 4) width = (s->img_x + 1) >> 1;
-      else if (bpp == 8) width = s->img_x;
+      stbi__skip(s, info.offset - 14 - info.hsz - psize * (info.hsz == 12 ? 3 : 4));
+      if (info.bpp == 4) width = (s->img_x + 1) >> 1;
+      else if (info.bpp == 8) width = s->img_x;
       else { STBI_FREE(out); return stbi__errpuc("bad bpp", "Corrupt BMP"); }
       pad = (-width)&3;
       for (j=0; j < (int) s->img_y; ++j) {
          for (i=0; i < (int) s->img_x; i += 2) {
             int v=stbi__get8(s),v2=0;
-            if (bpp == 4) {
+            if (info.bpp == 4) {
                v2 = v & 15;
                v >>= 4;
             }
@@ -4721,7 +4754,7 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
             out[z++] = pal[v][2];
             if (target == 4) out[z++] = 255;
             if (i+1 == (int) s->img_x) break;
-            v = (bpp == 8) ? stbi__get8(s) : v2;
+            v = (info.bpp == 8) ? stbi__get8(s) : v2;
             out[z++] = pal[v][0];
             out[z++] = pal[v][1];
             out[z++] = pal[v][2];
@@ -4733,14 +4766,14 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
       int rshift=0,gshift=0,bshift=0,ashift=0,rcount=0,gcount=0,bcount=0,acount=0;
       int z = 0;
       int easy=0;
-      stbi__skip(s, offset - 14 - hsz);
-      if (bpp == 24) width = 3 * s->img_x;
-      else if (bpp == 16) width = 2*s->img_x;
+      stbi__skip(s, info.offset - 14 - info.hsz);
+      if (info.bpp == 24) width = 3 * s->img_x;
+      else if (info.bpp == 16) width = 2*s->img_x;
       else /* bpp = 32 and pad = 0 */ width=0;
       pad = (-width) & 3;
-      if (bpp == 24) {
+      if (info.bpp == 24) {
          easy = 1;
-      } else if (bpp == 32) {
+      } else if (info.bpp == 32) {
          if (mb == 0xff && mg == 0xff00 && mr == 0x00ff0000 && ma == 0xff000000)
             easy = 2;
       }
@@ -4765,6 +4798,7 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
                if (target == 4) out[z++] = a;
             }
          } else {
+            int bpp = info.bpp;
             for (i=0; i < (int) s->img_x; ++i) {
                stbi__uint32 v = (bpp == 16 ? (stbi__uint32) stbi__get16le(s) : stbi__get32le(s));
                int a;

tests/image_test.c

@@ -7,7 +7,7 @@
 #define STB_DEFINE
 #include "stb.h"
 
-#define PNGSUITE_PRIMARY
+//#define PNGSUITE_PRIMARY
 
 #if 0
 void test_ycbcr(void)
@@ -65,7 +65,7 @@ int main(int argc, char **argv)
    int w,h;
    //test_ycbcr();
 
-   #if 1
+   #if 0
    // test hdr asserts
    for (h=0; h < 100; h += 2)
       for (w=0; w < 200; ++w)