stb_image: support for 1-bit BMP

stb_image.h

@@ -5007,7 +5007,6 @@ static void *stbi__bmp_parse_header(stbi__context *s, stbi__bmp_data *info)
    }
    if (stbi__get16le(s) != 1) return stbi__errpuc("bad BMP", "bad BMP");
    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");
@@ -5125,29 +5124,47 @@ static void *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int req
          pal[i][3] = 255;
       }
       stbi__skip(s, info.offset - 14 - info.hsz - psize * (info.hsz == 12 ? 3 : 4));
-      if (info.bpp == 4) width = (s->img_x + 1) >> 1;
+      if (info.bpp == 1) width = (s->img_x + 7) >> 3;
+      else 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 (info.bpp == 4) {
-               v2 = v & 15;
-               v >>= 4;
+      if (info.bpp == 1) {
+         for (j=0; j < (int) s->img_y; ++j) {
+            int bit_offset = 7, v = stbi__get8(s);
+            for (i=0; i < (int) s->img_x; ++i) {
+               int color = (v>>bit_offset)&0x1;
+               out[z++] = pal[color][0];
+               out[z++] = pal[color][1];
+               out[z++] = pal[color][2];
+               if((--bit_offset) < 0) {
+                  bit_offset = 7;
+                  v = stbi__get8(s);
+               }
             }
-            out[z++] = pal[v][0];
-            out[z++] = pal[v][1];
-            out[z++] = pal[v][2];
-            if (target == 4) out[z++] = 255;
-            if (i+1 == (int) s->img_x) break;
-            v = (info.bpp == 8) ? stbi__get8(s) : v2;
-            out[z++] = pal[v][0];
-            out[z++] = pal[v][1];
-            out[z++] = pal[v][2];
-            if (target == 4) out[z++] = 255;
+            stbi__skip(s, pad);
+         }
+      } else {
+         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 (info.bpp == 4) {
+                  v2 = v & 15;
+                  v >>= 4;
+               }
+               out[z++] = pal[v][0];
+               out[z++] = pal[v][1];
+               out[z++] = pal[v][2];
+               if (target == 4) out[z++] = 255;
+               if (i+1 == (int) s->img_x) break;
+               v = (info.bpp == 8) ? stbi__get8(s) : v2;
+               out[z++] = pal[v][0];
+               out[z++] = pal[v][1];
+               out[z++] = pal[v][2];
+               if (target == 4) out[z++] = 255;
+            }
+            stbi__skip(s, pad);
          }
-         stbi__skip(s, pad);
       }
    } else {
       int rshift=0,gshift=0,bshift=0,ashift=0,rcount=0,gcount=0,bcount=0,acount=0;