Homework 27

Module mash.py

Supports the creation a new image that is a mash up of two existing images — bg and fg. The new image has bg as its background. The pixels in fg that are dissimilar to the back screen color are copied on top of the background.

Primary function

combine( bg, fg, sx, sy, back_screen )

Returns mash up of background image bg and foreground image fg, where the pixels in fg that are dissimilar to back_screen are copied on top of the background.

The mash up uses location (sx, sy) as the spot in the background to start the lay over of fg.

Convenience functions

similar( p1, p2, max_allowable=THRESHOLD )

Returns whether the distance between pixels p1 and p2 is less than the max allowable threshold.

is_background( p, back_screen )

Returns whether p is similar to the back_screen color.

inbounds( spot, img )

Returns whether spot lies on img.

colorable( spot, img, p, back_screen )

Returns whether both spot is a location on img and color p is not similar to color back_screen.

from PIL import Image

helpful constants

THRESHOLD = 85 # default max allowable distance to be similar

GREEN = ( 0, 255, 0 ) # back screen color

def similar( p1, p2, max_allowable=THRESHOLD ) :

''' Returns whether pixels p1 and p2 have RGB differences less than the

    max allowable

'''

import color

pass

def is_background( p, back_screen ) :

''' Returns whether p is similar to the back_screen color

'''

pass

def inbounds( spot, img ) :

''' Returns whether spot lies on img

'''

pass

def colorable( spot, img, p, back_screen ) :

''' Returns whether both spot is a location on img and color p is not

    similar to color back_screen

'''

pass

def combine( bg, fg, sx, sy, back_screen ) :

''' Returns a new image that is a mash up of images bg and fg. The new

    image has bg as its background. The pixels in fg that are dissimilar

    to back_screen are copied on top of the background. The copy uses

    (sx, sy) as the spot in the background as the location to start the

    lay over of fg.

'''

bw, bh = bg.size

fw, fh = fg.size

new_image = bg.copy().convert( 'RGB' )

for fx in range( 0, fw ) :

    for fy in range( 0, fh ):

        fspot = ( fx, fy )

        fpixel = fg.getpixel( fspot )

        bx = sx + fx

        by = sy + fy

        bspot = ( bx, by )

        if ( colorable( bspot, bg, fpixel, back_screen ) ) :

            new_image.putpixel( bspot, fpixel )

return new_image

def clean_up( original, back_screen ) :

''' Returns a copy of original where pixels similar to the back_screen are set

    to the back_screen

'''

new_image = original.copy().convert( 'RGB' )

nw, nh = new_image.size

for nx in range( 0, nw ) :

    for ny in range( 0, nh ) :

        nspot = ( nx, ny )

        npixel = new_image.getpixel( nspot )

        if ( similar( npixel, back_screen ) ) :

            new_image.putpixel( nspot, back_screen )

return new_image

if ( name == 'main' ) :

import smashing

smashing.test_with_dino()

smashing.test_with_beyonce()

smashing.test_with_ww()

Resources from previous semesters are available.