automatically resizes and crops an image to make it suitable for use as a wallpaper. -- written by @coleifer

wallfix.py

#!/usr/bin/env python

import os
import re
import sys

from PIL import Image

HOME = os.environ['HOME']

try:
    screen_info = os.popen('xrandr').readlines()
    resolution_re = re.compile('\s+(\d+)x(\d+)\s+\d+\.\d+\*')
    for line in screen_info:
        match_obj = resolution_re.search(line)
        if match_obj:
            WIDTH, HEIGHT = map(int, match_obj.groups())
            break
except:
    WIDTH = 1440
    HEIGHT = 900
RATIO = float(WIDTH) / HEIGHT

def local_file(filename):
    return os.path.join(HOME, filename)

def make_wallpapers(original):
    im = Image.open(original)
    width, height = im.size
    ratio = float(width) / height

    if ratio > RATIO:
        # resize to match height, then crop horizontally from center
        new_width = int(HEIGHT * ratio)
        im.thumbnail((new_width, HEIGHT), Image.ANTIALIAS)
        offset = (new_width - WIDTH) / 2
        cropped = im.crop((offset, 0, offset + WIDTH, HEIGHT))
    elif ratio < RATIO:
        # resize to match width, then crop vertically from center
        new_height = int(WIDTH / ratio)
        im.thumbnail((WIDTH, new_height), Image.ANTIALIAS)
        offset = (new_height - HEIGHT) / 2
        cropped = im.crop((0, offset, WIDTH, offset + HEIGHT))
    else:
        im.thumbnail((WIDTH, HEIGHT), Image.ANTIALIAS)
        cropped = im

    path, ext = os.path.splitext(original)
    dest_jpg = local_file('.wallpaper.jpg')
    dest_png = local_file('.wallpaper.png')

    cropped.save(dest_jpg, 'JPEG', quality=100)
    cropped.save(dest_png, 'PNG')

def panic(msg):
    print >> sys.stderr, msg
    sys.exit(1)

if __name__ == '__main__':
    if len(sys.argv) != 2:
        panic('Error, missing required image file')

    filename = sys.argv[-1]
    if not os.path.exists(filename):
        panic('Error, file %s not found' % filename)

    make_wallpapers(filename)