sclass IICheckerBoard implements IIntegralImage {
  int w = 256, h = 256;
  double cols = 8, rows = 8;
  RGB color1 = RGB(Color.black), color2 = RGB(Color.white);
  
  public int getWidth() { ret w; }
  public int getHeight() { ret h; }
  
  public double getIntegralValue(int x, int y, int channel) {
    double col = doubleRatio(x, w)*cols/2;
    double row = doubleRatio(x, h)*rows/2;
    double xlow = frac(col), ylow = frac(row);
    ret rgbInt(color1, channel)*(ifloor(col)*.5 + ...)
  }
}