#enhance the contrast of a picture by making the
#brights brighter, the darks darker.

#The simple algorithm here is to take a color
#component m between 0 and 255, then replace
#m by 0 if m<64, replace m by 255 if m>=192,
#and otherwise replace m by 2*(m-64)

def increase_contrast(p):
  for px in getPixels(p):
    setRed(px,contr(getRed(px)))
    setBlue(px,contr(getBlue(px)))
    setGreen(px,contr(getGreen(px)))

def contr(m):
  if m< 64:
    u=0
  elif m>=192:
    u=255
  else:
    u=2*(m-64)
  return u