[safesixel] libncsixel_explode()

src/sixel/sixel.c

@@ -43,6 +43,155 @@ sixel* libncsixel_encode(sixelctx* sctx, const char* file, unsigned colorregs){
   return NULL;
 }
 
+uint32_t* libncsixel_explode(const sixel* s){
+  uint32_t* rgba = malloc(sizeof(*rgba) * s->pixy * s->pixx);
+  if(rgba == NULL){
+    return NULL;
+  }
+  uint32_t* colors = malloc(sizeof(*colors) * s->colorregs_used);
+  if(colors == NULL){
+    free(rgba);
+    return NULL;
+  }
+  const char* sx = s->escape;
+  // first we skip the header
+  while(*sx != '#'){
+    ++sx;
+  }
+  // now we build the color table (form: #Pc;Pu;Px;Py;Pz). data starts with
+  // a color spec lacking a semicolon.
+  enum {
+    STATE_WANT_HASH,
+    STATE_WANT_COLOR,
+    STATE_WANT_COLORSEMI,
+    STATE_WANT_COLORSPACE,
+    STATE_WANT_DATA,
+  } state = STATE_WANT_HASH;
+  unsigned color = 0;
+  unsigned x = 0;
+  unsigned y = 0;
+  unsigned rle = 1;
+  while(*sx){
+    if(*sx == '\e'){
+      break;
+    }
+    if(state == STATE_WANT_HASH){
+      if('#' != *sx){
+        goto err;
+      }
+      state = STATE_WANT_COLOR;
+    }else if(state == STATE_WANT_COLOR){
+      if(!isdigit(*sx)){
+        goto err;
+      }
+      color = 0;
+      do{
+        color *= 10;
+        color += *sx - '0';
+        ++sx;
+      }while(isdigit(*sx));
+//std::cerr << "Got color " << color << std::endl;
+      --sx;
+      state = STATE_WANT_COLORSEMI;
+    }else if(state == STATE_WANT_COLORSEMI){
+      // if we get a semicolon, we're a colorspec, otherwise data
+      if(*sx == ';'){
+        state = STATE_WANT_COLORSPACE;
+      }else{
+        state = STATE_WANT_DATA;
+        rle = 1;
+      }
+    }else if(state == STATE_WANT_COLORSPACE){
+      if('2' != *(sx++)){
+        goto err;
+      }
+      if(';' != *(sx++)){
+        goto err;
+      }
+      int r = 0;
+      do{
+        r *= 10;
+        r += *sx - '0';
+        ++s;
+      }while(isdigit(*sx));
+      if(';' != *(sx++)){
+        goto err;
+      }
+      int g = 0;
+      do{
+        g *= 10;
+        g += *sx - '0';
+        ++sx;
+      }while(isdigit(*sx));
+      if(';' != *(sx++)){
+        goto err;
+      }
+      int b = 0;
+      do{
+        b *= 10;
+        b += *sx - '0';
+        ++sx;
+      }while(isdigit(*sx));
+      uint32_t rgb = htole(0xff000000 + (r << 16u) * 255 / 100 + (g << 8u) * 255 / 100 + b * 255 / 100);
+//std::cerr << "Got color " << color << ": " << r << "/" << g << "/" << b << std::endl;
+      if(color >= s->colorregs_used){
+        goto err;
+      }
+      colors[color] = rgb;
+      state = STATE_WANT_HASH;
+      --sx;
+    }
+    // read until we hit next colorspec
+    if(state == STATE_WANT_DATA){
+//std::cerr << "Character " << *sx << std::endl;
+      if(*sx == '#'){
+        state = STATE_WANT_HASH;
+        --sx;
+      }else if(*sx == '!'){ // RLE
+        ++sx;
+        rle = 0;
+        do{
+          rle *= 10;
+          rle += *sx - '0';
+          ++sx;
+        }while(isdigit(*sx));
+        if(2 >= rle){
+          goto err;
+        }
+        --sx;
+      }else if(*sx == '$'){
+        x = 0;
+        state = STATE_WANT_HASH;
+      }else if(*sx == '-'){
+        x = 0;
+        y += 6;
+        state = STATE_WANT_HASH;
+      }else{
+//std::cerr << "RLE: " << rle << " pos: " << y << "*" << x << std::endl;
+        for(unsigned xpos = x ; xpos < x + rle ; ++xpos){
+          for(unsigned ypos = y ; ypos < y + 6 ; ++ypos){
+            if((*sx - 63) & (1u << (ypos - y))){
+              // ought be an empty pixel
+//std::cerr << *s << " BMAP[" << ypos << "][" << xpos << "] = " << std::hex << colors[color] << std::dec << std::endl;
+              rgba[ypos * s->pixx + xpos] = colors[color];
+            }
+          }
+        }
+        x += rle;
+        rle = 1;
+      }
+    }
+    ++sx;
+  }
+  free(colors);
+  return rgba;
+
+err:
+  free(rgba);
+  free(colors);
+  return NULL;
+}
+
 void libncsixel_stop(sixelctx* sctx){
   if(sctx){
     notcurses_stop(sctx->nc);