"""
CS 101 image manipulation examples
"""

from PIL import Image

def justBlue(image):
    """Return a new image containing just the blue values from an image.

    The input should be a PIL image object created using something like
    image = Image.open(filename), where filename is a string.
    """
    # create a copy of the original image so we don't lose the original
    newImage = image.copy()

    # create our 2D structure of pixels from the image so we can work with individual pixels
    pixels = newImage.load()

    # get the bounding box -- this is returned as a tuple and we use some python
    # magic to automatically break the tuple up into four variables
    minX,minY,width,height = image.getbbox()

    # iterate over every pixel in the image
    for y in range(height): 
        for x in range(width): 
            # get the rgb value of the pixel (as a tuple in the order (red, green, blue))
            rgb = pixels[x,y]

            # set the pixel to a new RGB value (in this instance, we keep the original
            # blue value and set the red and green to 0)
            pixels[x,y] = (0,0, rgb[2])

    # return the new image
    return newImage

def grayscale(image):
    """Return a new grayscale version of an image.

    The input should be a PIL image object created using something like
    image = Image.open(filename), where filename is a string.
    """
    # create a copy of the original image so we don't lose the original
    newImage = image.copy()

    # create our 2D structure of pixels from the image so we can work with individual pixels
    pixels = newImage.load()

    # get the bounding box -- this is returned as a tuple and we use some python
    # magic to automatically break the tuple up into four variables
    minX,minY,width,height = image.getbbox()

    # iterate over every pixel in the image
    for y in range(height):
        for x in range(width):
            # get the rgb value of the pixel (as a tuple in the order (red, green, blue))
            rgb = pixels[x,y]

            # set the pixel to a new RGB value 
            # average of red, green, blue
            avg = int((rgb[0] + rgb[1] + rgb[2]) / 3)
            pixels[x,y] = (avg, avg, avg)

    # return the new image
    return newImage

"""
Example usage in the shell:
>>> img1 = Image.open('statue.jpg')
>>> img1_gray = grayscale(img1)
>>> img1_gray.show()
>>> img1_gray.save('statue_gray.png')
"""