Source code for rgb2gray

"""Module for converting an image to gray value. Call this module by:

   im = convert_to_gray(filename)
   
   which will return a new image by converting all the pixes in the input file to gray scale.

"""

import Image

        
def convert_to_gray(filename):
    """Convert the image to a 2x2 array of pixels. Then read each
    pixel, convert its color to gray scale and copy to the pixel array
    of the output image. Return the resulting image.
    
    """
    
    im = Image.open(filename)
    w,h = im.size

    pics = im.load()

    im_copy = Image.new("RGB", (w,h))
    pics_copy = im_copy.load()

    for i in range(0,w-1):
        for j in range(0,h-1):
            color = pics[i,j]
            gray_val = (color[0]+color[1]+color[2])/3
            pics_copy[i,j] = (gray_val, gray_val, gray_val)
                    
    return im_copy