'''
  images.py

  Jeff Ondich, 1 Nov 2009
  
  This program illustrates pixel-based manipulation of images using PIL.
  To run this program, you need to install PIL (the Python Imaging Library),
  which you can get from http://www.pythonware.com/products/pil/ if it's
  not already installed on the computer you are using.  It is already
  installed in the CS labs in the CMC.

  You can find instructions for installing PIL on your computer at
  http://apps.carleton.edu/curricular/cs/resources/source/PILinstallation/.

  Your job for the image processing assignment is to write the functions
  below whose definitions currently contain only the stub code
  "return originalImage".  Simple testing code for all the functions,
  including the stubs, is included at the bottom of this program.
'''

import sys
import Image

def getGreenImage(originalImage):
    '''Returns a copy of the specified image with all the
       red and blue removed.'''
    greenImage = originalImage.copy()
    greenPixels = greenImage.load()
    imageWidth = greenImage.size[0]
    imageHeight = greenImage.size[1]
    for y in range(imageHeight):
        for x in range(imageWidth):
            greenValue = greenPixels[x, y][1]
            greenPixels[x, y] = (0, greenValue, 0)

    return greenImage

def getSmallImage(originalImage):
    '''Returns a copy of the specified image, scaled to half
       size both horizontally and vertically.'''
    smallImageWidth = originalImage.size[0] / 2
    smallImageHeight = originalImage.size[1] / 2
    originalPixels = originalImage.load()
    smallImage = Image.new("RGB", (smallImageWidth, smallImageHeight))
    smallImagePixels = smallImage.load()
    for y in range(smallImageHeight):
        for x in range(smallImageWidth):
            red = (originalPixels[2*x, 2*y][0] + originalPixels[2*x + 1, 2*y][0]\
                    + originalPixels[2*x, 2*y + 1][0] + originalPixels[2*x + 1, 2*y + 1][0]) / 4
            green = (originalPixels[2*x, 2*y][1] + originalPixels[2*x + 1, 2*y][1]\
                    + originalPixels[2*x, 2*y + 1][1] + originalPixels[2*x + 1, 2*y + 1][1]) / 4
            blue = (originalPixels[2*x, 2*y][2] + originalPixels[2*x + 1, 2*y][2]\
                    + originalPixels[2*x, 2*y + 1][2] + originalPixels[2*x + 1, 2*y + 1][2]) / 4
            smallImagePixels[x, y] = (red, green, blue)

    return smallImage

def getGrayImage(originalImage):
    '''Returns a copy of the specified image in black-and-white.'''
    return originalImage

def getMirrorImage(originalImage):
    '''Returns a copy of the specified image, reflected horizontally
       (so, for example, if there were a ">" in the original image,
       it would appear as a "<" in the mirror image).'''
    return originalImage

def getRotatedImage(originalImage):
    '''Returns a copy of the specified image, rotated clockwise
       by 90 degrees.  (Note that you will need to create a new
       image whose dimensions are different than the original
       image's dimensions.  See getSmallImage for an example of
       how to do this.)'''
    return originalImage


# Main program.
if __name__ == '__main__':
    if len(sys.argv) != 2:
        print 'Usage: %s imageFile' % sys.argv[0]
        exit()

    imageFileName = sys.argv[1]
    image = Image.open(imageFileName)
    image.show()

    greenImage = getGreenImage(image)
    greenImage.show()

    smallImage = getSmallImage(image)
    smallImage.show()

    grayImage = getGrayImage(image)
    grayImage.show()

    mirrorImage = getMirrorImage(image)
    mirrorImage.show()

    rotatedImage = getRotatedImage(image)
    rotatedImage.show()