anchor.diff:   * Create a mask describing the 4-connected shape containing [x],[y] in the image [src]
    */
   
  -Uint8List maskFlood(Image src, int x, int y, {threshold=0.0, compareAlpha=false}) {
  +Uint8List maskFlood(Image src, int x, int y, {num threshold=0.0, bool compareAlpha=false}) {
     int srcColor = src.getPixel(x, y);
     if (!compareAlpha) srcColor = setAlpha(srcColor, 0);
     Uint8List ret = Uint8List(src.width * src.height);
  
positive.code:  * Fill the 4-connected shape containing [x],[y] in the image [src] with the given [color]
   */
  
  Image fillFlood(Image src, int x, int y, int color, {threshold=0.0, compareAlpha=false}) {
    int srcColor = src.getPixel(x, y);
    if (!compareAlpha) srcColor = setAlpha(srcColor, 0);
  
  
negative.code:   return ret;
  }
  
  bool _testPixelLabColorDistance(Image src, int x, int y, List<double> refColor, num threshold) {
    int pixel = src.getPixel(x, y);
    bool compareAlpha = refColor.length > 3;
    List<double> pixelColor = rgbToLab(getRed(pixel), getGreen(pixel), getBlue(pixel));
  