docs: public int filterRGB(int pX, int pY, int pARGB) {
          // Get color components
          int r = pARGB >> 16 & 0xFF;
          int g = pARGB >>  8 & 0xFF;
          int b = pARGB       & 0xFF;
  
          // ITU standard:  Gray scale=(222*Red+707*Green+71*Blue)/1000
          int gray = (222 * r + 707 * g + 71 * b) / 1000;
  
          //int gray = (int) ((float) (r + g + b) / 3.0f);
  
          if (range != 1.0f) {
              // Apply range
              gray =  low + (int) (gray * range);
          }
  
          // Return ARGB pixel
          return  (pARGB & 0xFF000000) | (gray << 16) | (gray << 8) | gray;
      }