Added --lossy option

include/lcdfgif/gif.h

@@ -146,6 +146,7 @@ typedef		void (*Gif_ReadErrorHandler)(Gif_Stream* gfs,
 
 typedef struct {
     int flags;
+    int loss;
     void *padding[7];
 } Gif_CompressInfo;
 

src/giffunc.c

@@ -800,6 +800,7 @@ void
 Gif_InitCompressInfo(Gif_CompressInfo *gcinfo)
 {
     gcinfo->flags = 0;
+    gcinfo->loss = 0;
 }
 
 

src/gifsicle.c

@@ -191,6 +191,7 @@ static const char *output_option_types[] = {
 #define GRAY_OPT		369
 #define RESIZE_METHOD_OPT	370
 #define RESIZE_COLORS_OPT	371
+#define LOSSY_OPT		372
 
 #define LOOP_TYPE		(Clp_ValFirstUser)
 #define DISPOSAL_TYPE		(Clp_ValFirstUser + 1)
@@ -255,6 +256,7 @@ const Clp_Option options[] = {
 
   { "logical-screen", 'S', LOGICAL_SCREEN_OPT, DIMENSIONS_TYPE, Clp_Negate },
   { "loopcount", 'l', 'l', LOOP_TYPE, Clp_Optional | Clp_Negate },
+  { "lossy", 0, LOSSY_OPT, Clp_ValInt, Clp_Optional },
 
   { "merge", 'm', 'm', 0, 0 },
   { "method", 0, COLORMAP_ALGORITHM_OPT, COLORMAP_ALG_TYPE, 0 },
@@ -1901,6 +1903,13 @@ main(int argc, char *argv[])
       }
       break;
 
+    case LOSSY_OPT:
+      if (clp->have_val)
+        gif_write_info.loss = clp->val.i;
+      else
+        gif_write_info.loss = 20;
+      break;
+
       /* RANDOM OPTIONS */
 
      case NO_WARNINGS_OPT:

src/gifwrite.c

@@ -288,10 +288,8 @@ struct selected_node {
   Gif_Node *node; unsigned long pos, diff;
 };
 
-struct selected_node gfc_lookup_lossy(Gif_Node *work_node, Gif_CodeTable *gfc, const Gif_Colormap *gfcm, Gif_Image *gfi, int pos, unsigned long base_diff, struct rgb dither)
+struct selected_node gfc_lookup_lossy(Gif_Node *work_node, Gif_CodeTable *gfc, const Gif_Colormap *gfcm, Gif_Image *gfi, unsigned pos, unsigned long base_diff, struct rgb dither, const int max_diff)
 {
-  const int max_diff = (1L<<8); // That controls quality
-
   unsigned image_endpos = gfi->width * gfi->height;
   if (pos >= image_endpos) return (struct selected_node){work_node, pos, base_diff};
 
@@ -303,13 +301,13 @@ struct selected_node gfc_lookup_lossy(Gif_Node *work_node, Gif_CodeTable *gfc, c
   if (!node) {
     int i;
     if (&gfc->nodes[suffix]) { // prefix of the new node must be same as suffix of previously added node
-      return gfc_lookup_lossy(&gfc->nodes[suffix], gfc, gfcm, gfi, pos+1, base_diff, (struct rgb){0,0,0});
+      return gfc_lookup_lossy(&gfc->nodes[suffix], gfc, gfcm, gfi, pos+1, base_diff, (struct rgb){0,0,0}, max_diff);
     }
     for(i=0; i < gfc->clear_code; i++) {
       if (!&gfc->nodes[i]) continue;
       int diff = color_diff(gfcm, suffix, i, dither);
       if (diff <= max_diff) {
-        t = gfc_lookup_lossy(&gfc->nodes[i], gfc, gfcm, gfi, pos+1, base_diff + diff, color_diff_rgb(gfcm, suffix, i));
+        t = gfc_lookup_lossy(&gfc->nodes[i], gfc, gfcm, gfi, pos+1, base_diff + diff, color_diff_rgb(gfcm, suffix, i), max_diff);
         if (t.pos > best_t.pos || (t.pos == best_t.pos && t.diff < best_t.diff)) {
           best_t = t;
         }
@@ -322,7 +320,7 @@ struct selected_node gfc_lookup_lossy(Gif_Node *work_node, Gif_CodeTable *gfc, c
       if (!node->child.m[i]) continue;
       int diff = color_diff(gfcm, suffix, i, dither);
       if (diff <= max_diff) {
-        t = gfc_lookup_lossy(node->child.m[i], gfc, gfcm, gfi, pos+1, base_diff + diff,  color_diff_rgb(gfcm, suffix, i));
+        t = gfc_lookup_lossy(node->child.m[i], gfc, gfcm, gfi, pos+1, base_diff + diff,  color_diff_rgb(gfcm, suffix, i), max_diff);
         if (t.pos > best_t.pos || (t.pos == best_t.pos && t.diff < best_t.diff)) {
           best_t = t;
         }
@@ -333,7 +331,7 @@ struct selected_node gfc_lookup_lossy(Gif_Node *work_node, Gif_CodeTable *gfc, c
     for (node = node->child.s; node; node = node->sibling) {
       int diff = color_diff(gfcm, suffix, node->suffix, dither);
       if (diff <= max_diff) {
-        t = gfc_lookup_lossy(node, gfc, gfcm, gfi, pos+1, base_diff + diff,  color_diff_rgb(gfcm, suffix, node->suffix));
+        t = gfc_lookup_lossy(node, gfc, gfcm, gfi, pos+1, base_diff + diff,  color_diff_rgb(gfcm, suffix, node->suffix), max_diff);
         if (t.pos > best_t.pos || (t.pos == best_t.pos && t.diff < best_t.diff)) {
           best_t = t;
         }
@@ -358,8 +356,6 @@ static int
 write_compressed_data(Gif_Stream *gfs, Gif_Image *gfi,
 		      int min_code_bits, Gif_CodeTable *gfc, Gif_Writer *grr)
 {
-  uint8_t lossy = 1;
-
   uint8_t stack_buffer[232];
   uint8_t *buf = stack_buffer;
   unsigned bufpos = 0;
@@ -405,7 +401,7 @@ write_compressed_data(Gif_Stream *gfs, Gif_Image *gfi,
   Gif_Colormap *gfcm;
 
   pos = clear_pos = clear_bufpos = 0;
-  if (lossy) {
+  if (grr->gcinfo.loss) {
     image_endpos = gfi->height * gfi->width;
     gfcm = (gfi->local ? gfi->local : gfs->global);
   } else {
@@ -466,9 +462,9 @@ write_compressed_data(Gif_Stream *gfs, Gif_Image *gfi,
 
     /*****
      * Find the next code to output. */
-    if (lossy) {
+    if (grr->gcinfo.loss) {
       int lastpos = pos;
-      struct selected_node t = gfc_lookup_lossy(0, gfc, gfcm, gfi, pos, 0, (struct rgb){0,0,0});
+      struct selected_node t = gfc_lookup_lossy(0, gfc, gfcm, gfi, pos, 0, (struct rgb){0,0,0}, grr->gcinfo.loss * 10);
       pos = t.pos;
       work_node = t.node;
       run = pos - lastpos - 1;

src/support.c

@@ -214,6 +214,8 @@ Whole-GIF options: Also --no-OPTION.\n\
       --gamma G                 Set gamma for color reduction [2.2].\n");
 #endif
   printf("\
+      --lossy[=STRENGTH]        Order pixel patterns to create smaller\n\
+                                GIFs at cost of artifacts and noise.\n\
       --resize WxH              Resize the output GIF to WxH.\n\
       --resize-width W          Resize to width W and proportional height.\n\
       --resize-height H         Resize to height H and proportional width.\n\