compress image with file size threshold

compress_image.py

# -*- coding: utf-8 -*-
# @Author: insaneyilin
# Python version 2.7
# Reference: https://www.cnblogs.com/li1992/p/10675769.html


import os
import sys
import argparse
import glob
from PIL import Image


def get_args():
    arg_parser = argparse.ArgumentParser()
    arg_parser.add_argument('src_dir', type=str, help='source directory')
    arg_parser.add_argument('dest_dir', type=str, help='destination directory')
    arg_parser.add_argument('--thresh', type=float, help='image size threshold in MB',
            default=1.0)
    return arg_parser.parse_args()


def get_out_filename(in_file, dest_dir):
    dir_path, filename = os.path.split(in_file)
    # fname, ext = os.path.splitext(filename)
    return os.path.join(dest_dir, filename)


def compress_image(in_file, out_file, size_thresh, step=10, quality=80):
    in_file_size = os.path.getsize(in_file)
    if in_file <= size_thresh:
        return in_file
    compressed_file_size = in_file_size
    while compressed_file_size > size_thresh:
        im = Image.open(in_file)
        im.save(out_file, quality=quality)
        if quality - step <= 0:
            break
        quality -= step
        compressed_file_size = os.path.getsize(out_file)
    return compressed_file_size


if __name__ == '__main__':
    args = get_args()
    print "source dir: {}".format(args.src_dir)
    print "destination dir: {}".format(args.dest_dir)
    print "image size threshold: {}".format(args.thresh)
    thresh_in_bytes = args.thresh * 1024.0 * 1024.0

    filenames = glob.glob('{}/*'.format(args.src_dir))
    for filename in filenames:
        with Image.open(filename) as img:
            img_filesize = os.path.getsize(filename)
            print "\n{} {} MB".format(filename, img_filesize/(1024.0**2))
            out_filename = get_out_filename(filename, args.dest_dir)
            if not os.path.exists(args.dest_dir):
                os.mkdir(args.dest_dir)
            out_file_size = compress_image(filename, out_filename, thresh_in_bytes)
            print "after compression: {} {} MB".format(out_filename, out_file_size/(1024.0**2))