''' Solution to Problem 9.  '''

from PIL import Image

def legal( v ) :
    # if v is negative, return 0, and if it's over 255, return 255. Otherwise, return itself

    if v < 0:
        return 0
    elif v > 255:
        return 255
    else:
        return v

def offset( pixel, x, y, z ) :

    r, g, b = pixel

    nr, ng, nb = r - x, g - y, b - z
    nr, ng, nb = legal(nr), legal(ng), legal(nb)

    npixel = (nr, ng, nb)

    return npixel

def shift( original, x, y, z ) :
    ow, oh = original.size  # get dimensions of original

    nw, nh = ow, oh  # determine dimensions of new image

    new_image = Image.new('RGB', (nw, nh))  # create new image

    for nx in range(0, nw):  # fill in every pixel of new image

        for ny in range(0, nh):
            nspot = (nx, ny)  # set spot to be filled in new image

            ospot = nspot  # determine corresponding spot in original

            opixel = original.getpixel(ospot)  # get pixel (color) at corresponding spot

            npixel = offset(opixel, x, y, z)  # determine pixel (color) for new image

            new_image.putpixel(nspot, npixel)  # set spot in new image

    return new_image  # return filled in new image

if ( __name__  == '__main__' ) :
    import url
    link = 'http://www.cs.virginia.edu/~cs1112/images/ml.png'
    original = url.get_image( link )

    try :
        print( legal( -1 ), legal( 125 ), legal( 256 ) )
    except :
        print( 'legal() blows up' )

    try :
        print( offset( ( 25, 0, 200 ), 25, -50, 75 ) )
    except :
        print( 'offset() blows up' )

    try :
        im = shift( original, 25, -50, 75 )
        im.show()
    except :
        print( 'shift() blows up' )