#This is designed to alter the Cookie Monster picture
#that we've often viewed in class, but it's been implemented
#as a generic function that takes all the pixels in an image
#that are close enough to blue and reddens them.

#How "close to blue" a pixel is will be measured by the built-in
#distance function that measures the distance between colors.
#The threshold distance is supplied as a parameter to the function.
#The result is an altered picture in which every "blue enough" pixel
#has its red component interchanged with its blue component.

#You may need to play around with the green component to get just the 
#right effect.

def blue_to_red(p,threshold):
  for px in getPixels(p):
    if distance(getColor(px),blue)<=threshold:
      r=getRed(px)
      b=getBlue(px)
      setRed(px,b)
      setBlue(px,r)