[quantization] use clumpbyte for o(1) color lookup in first pass #2503

dankamongmen · Dec 28, 2021 · 6ec660a · 6ec660a
1 parent df1d815
commit 6ec660a
Showing 1 changed file with 16 additions and 60 deletions.
diff --git a/src/lib/sixel.c b/src/lib/sixel.c
@@ -319,56 +319,12 @@ scrub_color_table(sprixel* s){
 // color is not in the table and the table is full. returns the proper
 // dtable index (*not* color index) otherwise.
 static int
-find_color(sixeltable* stab, unsigned char comps[static RGBSIZE]){
-  int i;
-  if(stab->map->colors){
-    int l, r;
-    // binary search over memcmp()-ordered color table
-    l = 0;
-    r = stab->map->colors - 1;
-    do{
-      i = l + (r - l) / 2;
-      const unsigned char* cmpie = stab->map->table + i * CENTSIZE;
-//fprintf(stderr, " %u/%u/%u %u/%u/%u L %d R %d m %d\n", comps[0], comps[1], comps[2], cmpie[0], cmpie[1], cmpie[2], l, r, i);
-      int cmp = memcmp(cmpie, comps, RGBSIZE);
-      if(cmp == 0){
-        return ctable_to_dtable(cmpie);
-      }
-      if(cmp < 0){
-        l = i + 1;
-      }else{ // key is smaller
-        r = i - 1;
-      }
-//fprintf(stderr, " BCMP: %d L %d R %d m: %d\n", cmp, l, r, i);
-    }while(l <= r);
-    if(r < 0){
-      i = 0;
-    }else if(l == stab->map->colors){
-      i = stab->map->colors;
-    }else{
-      i = l;
-    }
-    if(stab->map->colors == stab->colorregs){
-      return -1;
-    }
-    if(i < stab->map->colors){
-//fprintf(stderr, "INSERTING COLOR %u %u %u AT %d\n", comps[0], comps[1], comps[2], i);
-      memmove(stab->map->table + (i + 1) * CENTSIZE,
-              stab->map->table + i * CENTSIZE,
-              (stab->map->colors - i) * CENTSIZE);
-    }
-  }else{
-    i = 0;
-  }
-//fprintf(stderr, "NEW COLOR CONCAT %u %u %u AT %d\n", comps[0], comps[1], comps[2], i);
-  memcpy(stab->map->table + i * CENTSIZE, comps, RGBSIZE);
-  dtable_to_ctable(stab->map->colors, stab->map->table + i * CENTSIZE);
-  ++stab->map->colors;
-  return stab->map->colors - 1;
-  //return ctable_to_dtable(stab->map->table + i * CENTSIZE);
+find_color(sixeltable* stab, unsigned char key){
+  dtable_to_ctable(stab->map->colors, stab->map->table + key * CENTSIZE);
+  return ctable_to_dtable(stab->map->table + key * CENTSIZE);
 }
 
-static void
+static int32_t
 update_deets(uint32_t rgb, cdetails* deets){
   unsigned char comps[RGBSIZE];
   deets->sums[0] += ncpixel_r(rgb);
@@ -398,7 +354,7 @@ update_deets(uint32_t rgb, cdetails* deets){
       deets->lo[2] = comps[2];
     }
   }
-  ++deets->count;
+  return ++deets->count;
 }
 
 // goes through the needs_refresh matrix, and damages cells needing refreshing.
@@ -456,7 +412,6 @@ extract_color_table(const uint32_t* data, int linesize, int cols,
   const int begy = bargs->begy;
   const int cdimy = bargs->u.pixel.cellpxy;
   const int cdimx = bargs->u.pixel.cellpxx;
-  const uint32_t mask = 0xe0c0e0;
   int pos = 0; // pixel position
   unsigned char* rmatrix = bargs->u.pixel.spx->needs_refresh;
   for(int visy = begy ; visy < (begy + leny) ; visy += 6){ // pixel row
@@ -521,17 +476,18 @@ extract_color_table(const uint32_t* data, int linesize, int cols,
         if(rgba_trans_p(*rgb, bargs->transcolor)){
           continue;
         }
-        unsigned char comps[RGBSIZE];
-        break_sixel_comps(comps, *rgb, mask);
-        int didx = find_color(stab, comps);
-//fprintf(stderr, "DEETS %d %u %u %u (orig %u/%u/%u)\n", didx, comps[0], comps[1], comps[2], ncpixel_r(*rgb), ncpixel_g(*rgb), ncpixel_b(*rgb));
-        if(didx < 0){
-//fprintf(stderr, "FAILED FINDING COLOR AUGH 0x%02x\n", mask);
-          return -1;
-        }
+        // we form an eight-bit index by taking the top 3 MSBs of the red and
+        // green channels, and the top 2 MSBs of the blue channel (of the
+        // three, the human eye is least sensitive to blue).
+        unsigned char clumpbyte =
+          (ncpixel_r(*rgb) & 0xe0) |
+          ((ncpixel_g(*rgb) & 0xe0) >> 3) |
+          ((ncpixel_b(*rgb) & 0xc0) >> 6);
+        int didx = find_color(stab, clumpbyte);
         stab->map->data[didx * stab->map->sixelcount + pos] |= (1u << (sy - visy));
-        update_deets(*rgb, &stab->deets[didx]);
-//debug_color_table(stab);
+        if(update_deets(*rgb, &stab->deets[didx]) == 1){
+          ++stab->map->colors;
+        }
 //fprintf(stderr, "color %d pos %d: 0x%x\n", c, pos, stab->data[c * stab->map->sixelcount + pos]);
 //fprintf(stderr, " sums: %u %u %u count: %d r/g/b: %u %u %u\n", stab->deets[c].sums[0], stab->deets[c].sums[1], stab->deets[c].sums[2], stab->deets[c].count, ncpixel_r(*rgb), ncpixel_g(*rgb), ncpixel_b(*rgb));
       }