imgcrush

#!/usr/bin/env python3
# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Crush image files.

We try to shrink the image files by reencoding/stripping data losslessly.

We currently support png and jpg files.
"""

import logging
import multiprocessing
import os
from pathlib import Path
import sys

import libdot


# We pick a recent Chromium commit.  It doesn't change much so shouldn't matter.
# Updating to the latest version shouldn't cause problems.
CHROMIUM_REF = '85.0.4148.0'

# Full path to Chromium's png crush script.
PNG_CRUSHER_URL = ('https://chromium.googlesource.com/chromium/src/+/%s/tools/'
                   'resources/optimize-png-files.sh' % (CHROMIUM_REF,))

# Our local cache of the script.
PNG_CRUSHER = libdot.BIN_DIR / f'.png.crusher.{CHROMIUM_REF}'

# The tool used to crush jpeg images.
JPG_CRUSHER = 'jpegoptim'


def update_png_crusher():
    """Update our local cache of Chromium's png optimizer script."""
    if PNG_CRUSHER.exists():
        return

    for path in libdot.BIN_DIR.glob('.png.crusher.*'):
        path.unlink()

    libdot.fetch(f'{PNG_CRUSHER_URL}?format=TEXT', PNG_CRUSHER, b64=True)
    PNG_CRUSHER.chmod(0o755)


def run(path, cmd):
    """Run the |cmd| for the |path| file."""
    logging.info('Processing %s', path)
    libdot.run([str(x) for x in cmd], check=False)


def process_file(pool, path):
    """Crush |path| as makes sense.

    Jobs are thrown into the |pool|, but we don't currently bother checking
    their return values.  General life cycle management is handled by the pool.
    """
    if path.suffix in ('.png',):
        update_png_crusher()
        pool.apply_async(run, (path, [PNG_CRUSHER, path]))
    elif path.suffix in ('.jpg', '.jpeg'):
        pool.apply_async(run, (path, [JPG_CRUSHER, path]))
    else:
        logging.debug('Skipping unknown file type %s', path.suffix)


def process_dir(pool, topdir):
    """Process all the paths under |topdir|."""
    for root, dirs, files in os.walk(topdir):
        root = Path(root)

        # Not really needed, but makes things consistent.
        dirs.sort()
        files.sort()

        for path in files:
            process_file(pool, root / path)


def get_parser():
    """Get a command line parser."""
    parser = libdot.ArgumentParser(description=__doc__)
    parser.add_argument('paths', nargs='+', type=Path,
                        help='Image files or directories to crush.')
    return parser


def main(argv):
    """The main func!"""
    parser = get_parser()
    opts = parser.parse_args(argv)

    pool = multiprocessing.Pool()

    # We walk the top set of args by hand to deref links.
    for path in opts.paths:
        if path.is_dir():
            process_dir(pool, path)
        elif path.is_file():
            process_file(pool, path)

    pool.close()
    pool.join()


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))