#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
#
#This corrects the error in the first version by
#swapping in place.  It illustrates looping over 
#ranges
def mirror3():
  file=pickAFile()
  sourcepic=makePicture(file)
  height=getHeight(sourcepic)
  width=getWidth(sourcepic)
  for y in range(1,height):
    for x in range(1,width/2):
      px=getPixel(sourcepic,x,y)
      px2=getPixel(sourcepic,width+1-x,y)
      saveColor=getColor(px2)
      setColor(px2,getColor(px))
      setColor(px,saveColor)
  show(sourcepic)