drastic image loading optimization

src/kernel/userland/browser.c

@@ -340,23 +340,38 @@ static void decode_image(unsigned char *data, int len, RenderElement *el) {
             el->img_current_frame = 0;
             el->next_frame_tick = sys_system(16, 0, 0, 0, 0) + (delays[0] * 60 / 1000);
             
+            uint32_t step_x = (img_w_orig << 16) / fit_w;
+            uint32_t step_y = (img_h_orig << 16) / fit_h;
+
             for (int i = 0; i < frame_count; i++) {
                 el->img_frames[i] = malloc(fit_w * fit_h * sizeof(uint32_t));
                 if (el->img_frames[i]) {
                     unsigned char *src_frame = rgba + (i * img_w_orig * img_h_orig * 4);
+                    uint16_t *src_h_table = malloc(fit_h * sizeof(uint16_t));
+                    uint16_t *src_w_table = malloc(fit_w * sizeof(uint16_t));
+                    
+                    if (src_h_table && src_w_table) {
+                        for (int y = 0; y < fit_h; y++) src_h_table[y] = (y * step_y) >> 16;
+                        for (int x = 0; x < fit_w; x++) src_w_table[x] = (x * step_x) >> 16;
+
                         for (int y = 0; y < fit_h; y++) {
-                        int sy = y * img_h_orig / fit_h;
+                            int sy = src_h_table[y];
+                            uint32_t src_row_off = sy * img_w_orig;
+                            uint32_t dst_row_off = y * fit_w;
                             for (int x = 0; x < fit_w; x++) {
-                            int sx = x * img_w_orig / fit_w;
+                                int sx = src_w_table[x];
-                            int idx = (sy * img_w_orig + sx) * 4;
+                                int idx = (src_row_off + sx) * 4;
                                 uint32_t r = src_frame[idx];
                                 uint32_t g = src_frame[idx+1];
                                 uint32_t b = src_frame[idx+2];
                                 uint32_t a = src_frame[idx+3];
-                            el->img_frames[i][y * fit_w + x] = (a << 24) | (r << 16) | (g << 8) | b;
+                                el->img_frames[i][dst_row_off + x] = (a << 24) | (r << 16) | (g << 8) | b;
                             }
                         }
                     }
+                    if (src_h_table) free(src_h_table);
+                    if (src_w_table) free(src_w_table);
+                }
                 el->img_delays[i] = delays[i];
             }
             el->img_w = fit_w; el->img_h = fit_h;
@@ -364,16 +379,20 @@ static void decode_image(unsigned char *data, int len, RenderElement *el) {
         } else {
             el->img_pixels = malloc(fit_w * fit_h * sizeof(uint32_t));
             if (el->img_pixels) {
+                uint32_t step_x = (img_w_orig << 16) / fit_w;
+                uint32_t step_y = (img_h_orig << 16) / fit_h;
                 for (int y = 0; y < fit_h; y++) {
-                    int sy = y * img_h_orig / fit_h;
+                    int sy = (y * step_y) >> 16;
+                    uint32_t src_row_off = sy * img_w_orig;
+                    uint32_t dst_row_off = y * fit_w;
                     for (int x = 0; x < fit_w; x++) {
-                        int sx = x * img_w_orig / fit_w;
+                        int sx = (x * step_x) >> 16;
-                        int idx = (sy * img_w_orig + sx) * 4;
+                        int idx = (src_row_off + sx) * 4;
                         uint32_t r = rgba[idx];
                         uint32_t g = rgba[idx+1];
                         uint32_t b = rgba[idx+2];
                         uint32_t a = rgba[idx+3];
-                        el->img_pixels[y * fit_w + x] = (a << 24) | (r << 16) | (g << 8) | b;
+                        el->img_pixels[dst_row_off + x] = (a << 24) | (r << 16) | (g << 8) | b;
                     }
                 }
                 el->img_w = fit_w; el->img_h = fit_h;

src/kernel/userland/stb_image.h

@@ -6669,19 +6669,27 @@ static void stbi__out_gif_code(stbi__gif *g, stbi__uint16 code)
 {
    stbi_uc *p, *c;
    int idx;
+   stbi__uint16 stack[4096];
+   int top = 0;
+   stbi__uint16 current = code;
 
-   // recurse to decode the prefixes, since the linked-list is backwards,
+   // Follow the chain of prefixes to the root, pushing suffixes onto the stack
-   // and working backwards through an interleaved image would be nasty
+   while (current != (stbi__uint16)-1) {
-   if (g->codes[code].prefix >= 0)
+      if (top >= 4096) break;
-      stbi__out_gif_code(g, g->codes[code].prefix);
+      stack[top++] = current;
+      current = (stbi__uint16)g->codes[current].prefix;
+   }
 
-   if (g->cur_y >= g->max_y) return;
+   // Pop and process suffixes in order
+   while (top > 0) {
+      stbi__uint16 c_code = stack[--top];
+      if (g->cur_y >= g->max_y) continue;
 
       idx = g->cur_x + g->cur_y;
       p = &g->out[idx];
       g->history[idx / 4] = 1;
 
-   c = &g->color_table[g->codes[code].suffix * 4];
+      c = &g->color_table[g->codes[c_code].suffix * 4];
       if (c[3] > 128) { // don't render transparent pixels;
          p[0] = c[2];
          p[1] = c[1];
@@ -6700,6 +6708,7 @@ static void stbi__out_gif_code(stbi__gif *g, stbi__uint16 code)
             --g->parse;
          }
       }
+   }
 }
 
 static stbi_uc *stbi__process_gif_raster(stbi__context *s, stbi__gif *g)
@@ -6963,15 +6972,46 @@ static stbi_uc *stbi__gif_load_next(stbi__context *s, stbi__gif *g, int *comp, i
    }
 }
 
-static void *stbi__load_gif_main_outofmem(stbi__gif *g, stbi_uc *out, int **delays)
+static int stbi__gif_count_frames(stbi__context *s)
 {
-   STBI_FREE(g->out);
+   int layers = 0;
-   STBI_FREE(g->history);
+   stbi_uc flags;
-   STBI_FREE(g->background);
+   int tag;
+   int off = s->read_from_callbacks ? 0 : (int)(s->img_buffer - s->img_buffer_original);
 
-   if (out) STBI_FREE(out);
+   stbi__skip(s, 6); // GIF87a/GIF89a
-   if (delays && *delays) STBI_FREE(*delays);
+   stbi__skip(s, 4); // w, h
-   return stbi__errpuc("outofmem", "Out of memory");
+   flags = stbi__get8(s);
+   stbi__skip(s, 2);
+   if (flags & 0x80) stbi__skip(s, 3 * (2 << (flags & 7)));
+
+   while (!stbi__at_eof(s)) {
+      tag = stbi__get8(s);
+      if (tag == 0x2C) {
+         layers++;
+         stbi__skip(s, 8);
+         flags = stbi__get8(s);
+         if (flags & 0x80) stbi__skip(s, 3 * (2 << (flags & 7)));
+         stbi__get8(s); // LZW size
+         while (1) {
+            int len = stbi__get8(s);
+            if (len == 0) break;
+            stbi__skip(s, len);
+         }
+      } else if (tag == 0x21) {
+         stbi__get8(s);
+         while (1) {
+            int len = stbi__get8(s);
+            if (len == 0) break;
+            stbi__skip(s, len);
+         }
+      } else if (tag == 0x3B) break;
+      else break;
+   }
+
+   stbi__rewind(s);
+   if (off) stbi__skip(s, off);
+   return layers;
 }
 
 static void *stbi__load_gif_main(stbi__context *s, int **delays, int *x, int *y, int *z, int *comp, int req_comp)
@@ -6983,17 +7023,28 @@ static void *stbi__load_gif_main(stbi__context *s, int **delays, int *x, int *y,
       stbi_uc *two_back = 0;
       stbi__gif g;
       int stride;
-      int out_size = 0;
+      int total_layers = 0;
-      int delays_size = 0;
-
-      STBI_NOTUSED(out_size);
-      STBI_NOTUSED(delays_size);
 
       memset(&g, 0, sizeof(g));
+
+      total_layers = stbi__gif_count_frames(s);
+      if (total_layers <= 0) return stbi__errpuc("no frames", "Corrupt GIF");
+
+      // Initial header parse to get dimensions
+      if (!stbi__gif_header(s, &g, comp, 0)) return 0;
+      stride = g.w * g.h * 4;
+      stbi__rewind(s); // Rewind again for the main loop
+
+      out = (stbi_uc*)stbi__malloc(total_layers * stride);
+      if (!out) return stbi__errpuc("outofmem", "Out of memory");
+      
       if (delays) {
-         *delays = 0;
+         *delays = (int*)stbi__malloc(total_layers * sizeof(int));
+         if (!*delays) { STBI_FREE(out); return stbi__errpuc("outofmem", "Out of memory"); }
       }
 
+      memset(&g, 0, sizeof(g)); // Reset for real load
+
       do {
          u = stbi__gif_load_next(s, &g, comp, req_comp, two_back);
          if (u == (stbi_uc *) s) u = 0;  // end of animated gif marker
@@ -7002,39 +7053,12 @@ static void *stbi__load_gif_main(stbi__context *s, int **delays, int *x, int *y,
             *x = g.w;
             *y = g.h;
             ++layers;
-            stride = g.w * g.h * 4;
             
-            if (out) {
+            if (layers > total_layers) break; // Defensive
-               void *tmp = (stbi_uc*) STBI_REALLOC_SIZED( out, out_size, layers * stride );
-               if (!tmp)
-                  return stbi__load_gif_main_outofmem(&g, out, delays);
-               else {
-                   out = (stbi_uc*) tmp;
-                   out_size = layers * stride;
-               }
 
-               if (delays) {
-                  int *new_delays = (int*) STBI_REALLOC_SIZED( *delays, delays_size, sizeof(int) * layers );
-                  if (!new_delays)
-                     return stbi__load_gif_main_outofmem(&g, out, delays);
-                  *delays = new_delays;
-                  delays_size = layers * sizeof(int);
-               }
-            } else {
-               out = (stbi_uc*)stbi__malloc( layers * stride );
-               if (!out)
-                  return stbi__load_gif_main_outofmem(&g, out, delays);
-               out_size = layers * stride;
-               if (delays) {
-                  *delays = (int*) stbi__malloc( layers * sizeof(int) );
-                  if (!*delays)
-                     return stbi__load_gif_main_outofmem(&g, out, delays);
-                  delays_size = layers * sizeof(int);
-               }
-            }
             memcpy( out + ((layers - 1) * stride), u, stride );
             if (layers >= 2) {
-               two_back = out - 2 * stride;
+               two_back = out + (layers - 2) * stride;
             }
 
             if (delays) {