first go at sixel blitter #200

src/lib/blit.c

@@ -853,7 +853,53 @@ sixel_blit(ncplane* nc, int placey, int placex, int linesize,
       return -1;
     }
     int visx = begx;
-    for(x = placex ; visx < (begx + lenx) && x < dimx ; ++x, visx += 2){
+    for(x = placex ; visx < (begx + lenx) && x < dimx ; ++x, visx += 1){
+      size_t offset = 0;
+      char sixel[128]; // FIXME
+      // FIXME find sixels with common colors for single register program
+      unsigned bitsused = 0; // once 63, we're done
+      int colorreg = 1; // leave 0 as background
+      for(int sy = y ; sy < dimy && sy < y + 6 ; ++sy){
+        const uint32_t* rgb = (const uint32_t*)(data + (linesize * sy) + (visx * 4));
+        if(ffmpeg_trans_p(ncpixel_a(*rgb))){
+          continue;
+        }
+        if(bitsused & (1u << (sy - y))){
+          continue;
+        }
+        unsigned thesebits = 1u << (sy - y);
+        for(int ty = sy + 1 ; ty < dimy && ty < y + 6 ; ++ty){
+          const uint32_t* trgb = (const uint32_t*)(data + (linesize * ty) + (visx * 4));
+          if(!ffmpeg_trans_p(ncpixel_a(*trgb))){
+            if(memcmp(rgb + 1, trgb + 1, 3) == 0){
+              thesebits |= (1u << (ty - y));
+            }
+          }
+        }
+        if(thesebits){
+          bitsused |= thesebits;
+          char c = 63 + thesebits;
+          // FIXME use percentages(rgb)
+          // bitstring is added to 63, resulting in [63, 126] aka '?'..'~'
+          int n = snprintf(sixel + offset, sizeof(sixel) - offset,
+                           "#%d;2;%d;%d;%d%c", colorreg, 100, 100, 100, c);
+          if(n < 0){
+            return -1;
+          }
+          offset += n;
+          ++colorreg;
+        }
+        if(bitsused == 63){
+          break;
+        }
+      }
+      if(offset){
+        nccell* c = ncplane_cell_ref_yx(nc, y, x);
+        if(pool_blit_direct(&nc->pool, c, sixel, offset, 1) <= 0){
+          return -1;
+        }
+        cell_set_pixels(c);
+      } // FIXME otherwise, reset?
     }
   }
   return total;
@@ -876,7 +922,7 @@ static const struct blitset notcurses_blitters[] = {
      .blit = tria_blit,      .name = "fourstep",      .fill = false, },
    { .geom = NCBLIT_BRAILLE, .width = 2, .height = 4, .egcs = L"⠀⢀⢠⢰⢸⡀⣀⣠⣰⣸⡄⣄⣤⣴⣼⡆⣆⣦⣶⣾⡇⣇⣧⣷⣿",
      .blit = braille_blit,   .name = "braille",       .fill = true,  },
-   { .geom = NCBLIT_PIXEL,   .width = 2, .height = 6, .egcs = L"",
+   { .geom = NCBLIT_PIXEL,   .width = 1, .height = 6, .egcs = L"",
      .blit = sixel_blit,     .name = "pixel",         .fill = true,  },
    { .geom = 0,              .width = 0, .height = 0, .egcs = NULL,
      .blit = NULL,           .name = NULL,            .fill = false,  },
@@ -973,6 +1019,14 @@ const struct blitset* lookup_blitset(const tinfo* tcache, ncblitter_e setid, boo
       return NULL;
     }
   }
+  // without pixel support, NCBLIT_PIXEL decays to NCBLIT_3x2
+  if(!tcache->pixelon && setid == NCBLIT_PIXEL){
+    if(may_degrade){
+      setid = NCBLIT_3x2;
+    }else{
+      return NULL;
+    }
+  }
   // without sextant support, NCBLIT_3x2 decays to NCBLIT_2x2
   if(!tcache->sextants && setid == NCBLIT_3x2){
     if(may_degrade){