sclass G22ColorWalker > G22Walker<IRGBImage> {
  // the ideal image it is looking for (set/get)
  int[] rememberedImage; // size visionW*visionH
  
  // only works when we already have a rememberedImage
  double scorePosition(Pt pos, IRGBImage image) {
    int vx = pos.x-visionW, vy = pos.y-visionH, i = 0;
    int diff = 0;
    for y to visionH:
      for x to visionW:
        diff += colorDistance(rememberedImage[i++], image.getIntPixel(vx+x, vy+y));
    ret -diff;
  }
  
  bool hasRememberedImage() { ret rememberedImage != null; }
  
  void rememberImage(IRGBImage image) {
    if (rememberedImage == null)
      rememberedImage = new int[visionW*visionH];
      
    int vx = visionX1(), vy = visionY1(), i = 0;
    for y to visionH:
      for x to visionW:
        rememberedImage[i++] = image.getIntPixel(vx+x, vy+y);
  }
}