generate resized bitmaps for each dpi

android_resize.py

#!/usr/bin/env python

import sys
import os
import Image

def resize(src_dir, dest_dir, num, den):
    if not os.path.exists(dest_dir):
        os.makedirs(dest_dir)
    files = os.listdir(src_dir)
    for fname in files:
        im = Image.open(os.path.join(src_dir,fname))
        im.thumbnail(
                (max(1, num * im.size[0] / den),
                 max(1, num * im.size[1] / den)), Image.ANTIALIAS)
        im.save(os.path.join(dest_dir, fname))

if __name__ == '__main__':
    if len(sys.argv) < 2:
        sys.stderr.write('android_resize.py target_directory [destination_directory]\n')
        sys.exit(1)

    src_dir = sys.argv[1]
    dest_dir = sys.argv[2] if 3 <= len(sys.argv) else './'
    if not os.path.exists(src_dir):
        sys.stderr.write('input directory does not exist\n')
        sys.exit(1)
    if not os.path.isdir(src_dir):
        sys.stderr.write('input should be a directory\n')
        sys.exit(1)

    # c.f. http://developer.android.com/guide/practices/screens_support.html
    resize(src_dir, os.path.join(dest_dir,  'drawable-ldpi'), 3, 8)
    resize(src_dir, os.path.join(dest_dir,  'drawable-mdpi'), 1, 2)
    resize(src_dir, os.path.join(dest_dir,  'drawable-hdpi'), 3, 4)
    resize(src_dir, os.path.join(dest_dir, 'drawable-xhdpi'), 1, 1)