#create the mirror image of a picture
#
#A little geometry:  The reflection of the
#pixel at position X,Y is the pixel at positon
#width+1-X,Y
def mirror():
  pic=makePicture(pickAFile())
  width=getWidth(pic)
  for px in getPixels(pic):
    x=getX(px)
    y=getY(px)
    px2=getPixel(pic,width+1-x,y)
    setColor(px2,getColor(px))
    setColor(px,getColor(px2))
  show(pic)