def f1():
   Picture = makeEmptyPicture(256,256)
   for colum in range(0,256):
     for row in range(0,256):
       px=getPixel(Picture,colum,row)
       xPos = getX(px)
       setRed (px,255-xPos)
       setGreen (px,0)
       setBlue (px,0)
       colour= getColor(px)
   show(Picture)