Cut time to optimize an image with many colors in half.

O(n^2) -> O(n).

src/kcolor.h

@@ -52,6 +52,15 @@ static inline kcolor kc_make8g(int a0, int a1, int a2) {
     return x;
 }
 
+/* return the kcolor representation of `*gfc` (no gamma transformation) */
+static inline kcolor kc_makegfc(const Gif_Color* gfc) {
+    kcolor kc;
+    kc.a[0] = (gfc->gfc_red << 8) + gfc->gfc_red;
+    kc.a[1] = (gfc->gfc_green << 8) + gfc->gfc_green;
+    kc.a[2] = (gfc->gfc_blue << 8) + gfc->gfc_blue;
+    return kc;
+}
+
 /* return the gamma transformation of `*gfc` */
 static inline kcolor kc_makegfcg(const Gif_Color* gfc) {
     return kc_make8g(gfc->gfc_red, gfc->gfc_green, gfc->gfc_blue);
@@ -208,7 +217,7 @@ typedef struct kchist {
 void kchist_init(kchist* kch);
 void kchist_cleanup(kchist* kch);
 void kchist_make(kchist* kch, Gif_Stream* gfs, uint32_t* ntransp);
-void kchist_add(kchist* kch, kcolor color, kchist_count_t count);
+kchistitem* kchist_add(kchist* kch, kcolor color, kchist_count_t count);
 void kchist_compress(kchist* kch);
 
 

src/optimize.c

@@ -9,6 +9,7 @@
 
 #include <config.h>
 #include "gifsicle.h"
+#include "kcolor.h"
 #include <assert.h>
 #include <string.h>
 
@@ -43,6 +44,8 @@ static int screen_height;
 
 /* Colormap containing all colors in the image. May have >256 colors */
 static Gif_Colormap *all_colormap;
+/* Histogram so we can find colors quickly */
+static kchist all_colormap_hist;
 
 /* The old global colormap, or a fake one we created if necessary */
 static Gif_Colormap *in_global_map;
@@ -86,36 +89,32 @@ delete_opt_data(Gif_OptData *od)
 }
 
 
-/* colormap_combine: Ensure that each color in 'src' is represented in 'dst'.
-   For each color 'i' in 'src', src->col[i].pixel == some j so that
-   GIF_COLOREQ(&src->col[i], &dst->col[j]). dst->col[0] is reserved for
-   transparency; no source color will be mapped to it. */
+/* all_colormap_add: Ensure that each color in 'src' is represented in
+   'all_colormap'. For each color 'i' in 'src', src->col[i].pixel == some j
+   so that GIF_COLOREQ(&src->col[i], &all_colormap->col[j]).
+   all_colormap->col[0] is reserved for transparency; no source color will
+   be mapped to it. */
 
-void
-colormap_combine(Gif_Colormap *dst, Gif_Colormap *src)
-{
-  Gif_Color *src_col, *dst_col;
-  int i, j;
+static void all_colormap_add(const Gif_Colormap* src) {
+    int i;
 
-  /* expand dst->col if necessary. This might change dst->col */
-  if (dst->ncol + src->ncol >= dst->capacity) {
-    dst->capacity *= 2;
-    Gif_ReArray(dst->col, Gif_Color, dst->capacity);
-  }
+    /* expand dst->col if necessary. This might change dst->col */
+    if (all_colormap->ncol + src->ncol >= all_colormap->capacity) {
+        all_colormap->capacity *= 2;
+        Gif_ReArray(all_colormap->col, Gif_Color, all_colormap->capacity);
+    }
 
-  src_col = src->col;
-  dst_col = dst->col;
-  for (i = 0; i < src->ncol; i++, src_col++) {
-    for (j = 1; j < dst->ncol; j++) {
-      if (GIF_COLOREQ(src_col, &dst_col[j]))
-	goto found;
+    for (i = 1; i < src->ncol; ++i) {
+        kchistitem* khi = kchist_add(&all_colormap_hist,
+                                     kc_makegfc(&src->col[i]), 0);
+        if (!khi->count) {
+            all_colormap->col[all_colormap->ncol] = src->col[i];
+            all_colormap->col[all_colormap->ncol].pixel = 0;
+            khi->count = all_colormap->ncol;
+            ++all_colormap->ncol;
+        }
+        src->col[i].pixel = khi->count;
     }
-    dst_col[j] = *src_col;
-    dst_col[j].pixel = 0;
-    dst->ncol++;
-   found:
-    src_col->pixel = j;
-  }
 }
 
 
@@ -367,17 +366,20 @@ initialize_optimizer(Gif_Stream *gfs)
   {
     int any_globals = 0;
     int first_transparent = -1;
+
+    kchist_init(&all_colormap_hist);
     for (i = 0; i < gfs->nimages; i++) {
       Gif_Image *gfi = gfs->images[i];
       if (gfi->local)
-	colormap_combine(all_colormap, gfi->local);
+	all_colormap_add(gfi->local);
       else
 	any_globals = 1;
       if (gfi->transparent >= 0 && first_transparent < 0)
 	first_transparent = i;
     }
     if (any_globals)
-      colormap_combine(all_colormap, in_global_map);
+      all_colormap_add(in_global_map);
+    kchist_cleanup(&all_colormap_hist);
 
     /* try and maintain transparency's pixel value */
     if (first_transparent >= 0) {

src/quantize.c

@@ -193,9 +193,10 @@ void kchist_cleanup(kchist* kch) {
     kch->h = NULL;
 }
 
-void kchist_add(kchist* kch, kcolor k, kchist_count_t count) {
+kchistitem* kchist_add(kchist* kch, kcolor k, kchist_count_t count) {
     unsigned hash1, hash2 = 0;
     kacolor ka;
+    kchistitem *khi;
     ka.k = k;
     ka.a[3] = 0;
 
@@ -206,8 +207,11 @@ void kchist_add(kchist* kch, kcolor k, kchist_count_t count) {
              | ((ka.a[1] & 0x7FE0) << 5)
              | ((ka.a[2] & 0x7FE0) >> 5)) % kch->capacity;
 
-    while (kch->h[hash1].count
-           && memcmp(&kch->h[hash1].ka, &ka, sizeof(ka)) != 0) {
+    while (1) {
+        khi = &kch->h[hash1];
+        if (!khi->count
+            || memcmp(&khi->ka, &ka, sizeof(ka)) == 0)
+            break;
         if (!hash2) {
             hash2 = (((ka.a[0] & 0x03FF) << 20)
                      | ((ka.a[1] & 0x03FF) << 10)
@@ -219,13 +223,14 @@ void kchist_add(kchist* kch, kcolor k, kchist_count_t count) {
             hash1 -= kch->capacity;
     }
 
-    if (!kch->h[hash1].count) {
-        kch->h[hash1].ka = ka;
+    if (!khi->count) {
+        khi->ka = ka;
         ++kch->n;
     }
-    kch->h[hash1].count += count;
-    if (kch->h[hash1].count < count)
-        kch->h[hash1].count = (kchist_count_t) -1;
+    khi->count += count;
+    if (khi->count < count)
+        khi->count = (kchist_count_t) -1;
+    return khi;
 }
 
 static void kchist_grow(kchist* kch) {