import ppm

#
# constants for accessing color components of pixels
#
RED = 0
GREEN = 1
BLUE = 2


#
#  Create a gray scale version of the image provided, returning a new
#  image.  The image passed as a parameter is not modified.
#
#  Parameters:  image (ppm format)
#
#  Returns: new image in greyscale
#
def grayscale(original):
  #
  #  Create a new image with the same dimensions as the original
  #
  gray = ppm.createImage(ppm.width(original), ppm.height(original))
  
  #
  #  Copy each pixel from the original and convert it to gray
  #
  #  For each pixel in the image
  for i in range(0, ppm.width(original)):
    for j in range(0, ppm.height(original)):
      avg = (original[i][j][RED] + original[i][j][GREEN] + original[i][j][BLUE]) / 3
      gray[i][j][RED] = avg
      gray[i][j][GREEN] = avg
      gray[i][j][BLUE] = avg

  return gray



#
#  Create a sepia tone version of the image provided, returning a new
#  image.  The image passed as a parameter is not modified.
#
#
#  Parameters:  image (ppm format)
#
#  Returns: new image in sepia
#
def sepia(original):
  #
  #  Create a new image with the same dimensions as the original
  #
  new_image = ppm.createImage(ppm.width(original), ppm.height(original))
  
  #
  #  Copy each pixel from the original and convert it to sepia
  #
  #  For each pixel in the image
  for i in range(0, ppm.width(original)):
    for j in range(0, ppm.height(original)):
      new_image[i][j][RED] = min(255, original[i][j][RED] * 0.393 + original[i][j][GREEN] * 0.769 + original[i][j][BLUE] * 0.189)
      new_image[i][j][GREEN] = min(255, original[i][j][RED] * 0.349 + original[i][j][GREEN] * 0.686 + original[i][j][BLUE] * 0.168)
      new_image[i][j][BLUE] = min(255, original[i][j][RED] * 0.272 + original[i][j][GREEN] * 0.534 + original[i][j][BLUE] * 0.131)

  return new_image


def main():
  #
  # make display window white
  #
  print "color 255 255 255"
  print "clear"
    
  dd = ppm.loadPPM("DonaldDuck.ppm")
  lion = ppm.loadPPM("Lion.ppm")

  #
  # display Donald Duck in upper left corner, lion underneath
  #
  ppm.displayImage(0,0,dd)
  ppm.displayImage(0,ppm.height(dd),lion)
    
  #
  #  Create the gray scale version of donald duck, display beside original
  #
  gray = grayscale(dd)
  ppm.displayImage(ppm.width(dd), 0, gray)  # display beside original
  
  #
  #  Create a sepia tone version of the lion, display beside original
  #
  sep = sepia(lion)
  ppm.displayImage(ppm.width(sep), ppm.height(dd), sep) # beside original

main()