generate ios assets from retina version (image@2x.png -> image.png)

iosasset.py

#!/usr/bin/env python
from PIL import Image
from argh import arg, dispatch_command
import os

def gen_assets(rootdir, force=False):
    for root, dirs, files in os.walk(rootdir):
        for d in dirs:
            gen_thumb(os.path.join(root, d), force=force)
        for f in files:
            if f.endswith('@2x.png') and not f.endswith('-568h@2x.png'):
                f = os.path.relpath(os.path.join(root, f))
                name = f.replace('@2x.png', '.png')
                if os.path.exists(name) and not force:
                    continue
                print '%s -> %s' % (f, name)
                img = Image.open(f)
                width, height = img.size
                img.thumbnail((width/2, height/2), Image.ANTIALIAS)
                img.save(name, "PNG")

@dispatch_command
@arg('ROOTDIR', default='.', help='Root directory for searching assets')
@arg('--force', '-f', default=False, help='Force generating assets. Will overwrite existing files.')
def main(args):
    gen_assets(args.ROOTDIR, force=args.force)