"wallfix", using python to set my wallpaper

I had fun writing about my "cd" helper, so I thought I'd share another productivity helper I wrote for setting my wallpaper. It's a little silly, but I insist on my wallpaper being used for my lockscreen and my login window as well -- that way the entire time I'm on my computer the background is "seamless". Before I wrote this script it used to take me probably 3 or 4 minutes to change wallpapers!

I use the following utilities on my desktop, so I needed a way to set the background for all of them:

Due to some quirks in the way all these tools work, I found that in order for my computer to always display the exact same background I needed to resize the image to be exactly the size of my desktop. This was additionally complicated by the fact that wallpapers come in different aspect ratios, so sometimes I would have to crop things as well. Lastly, for whatever reason, SLiM wants a .jpg while i3lock only takes a .png.

I needed to write a helper that would:

  1. Resize and crop the image to fit my screen size.
  2. Generate a .png and a .jpg
  3. Tell i3lock, SLiM and my desktop (feh) to use the right image.

The first step was I established ~/.wallpaper.jpg and ~/.wallpaper.png as the canonical location of my wallpaper images. I then updated SLiM, i3lock and feh to point at those images. Doing this means that I only need to write the images to once place and everything will just work!

Resizing and cropping

I wrote this script with python and used PIL to do the image manipulation. Here is the entire script:

#!/usr/bin/env python

import os
import sys

from PIL import Image

HOME = os.environ['HOME']

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')

if __name__ == '__main__':
    if len(sys.argv) == 1:
        filename = raw_input('New image? ')
    else:
        filename = sys.argv[-1]

    if not os.path.exists(filename):
        print 'Error: %s not found' % filename
        sys.exit(1)

    make_wallpapers(filename)

To use this, I just run wallfix ~/pictures/Wallpapers/kittens3.jpg and everything is set up!

The moral of the story

I think I spent 30 minutes setting this all up. If the amount of time it used to take me to change my wallpaper manually was 3 minutes, after 10 changes I'll have made up the time. More than the time saved, though, I think it's useful to be mindful of tasks you do that are repetitive and figure out how to automate them.

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