Generates resized images at various resolutions

gen_resized_images.py

#!/usr/bin/env python

from __future__ import print_function

import os
import subprocess

from glob import glob
from wand.image import Image

ROOT_PATH = os.path.dirname(os.path.abspath(__file__))
MEDIA_RESIZED_PATH = os.path.join(ROOT_PATH, 'media/resized')
MEDIA_PATH = os.path.join(ROOT_PATH, 'media')
MEDIA_GLOB = os.path.join(MEDIA_PATH, '**', '*.*')

RESIZE_WIDTHS = [720] #[360, 720, 2048]

LOG_VERBOSE = False

def make_resized_path(basepath, width, ext, suffix=''):
    return '%s_%dw%s%s' % (basepath, width, suffix, ext)

def subproc_or_die(args):
    if LOG_VERBOSE:
        print('\n' + ' '.join(args))
    subprocess.check_call(args)

def subproc(args):
    if LOG_VERBOSE:
        print('\n' + ' '.join(args))
    return subprocess.call(args)

for path in glob(MEDIA_GLOB):
    rootpath, ext = os.path.splitext(path)
    resized_base = os.path.join(MEDIA_RESIZED_PATH, os.path.relpath(rootpath, MEDIA_PATH))
    try:
        os.makedirs(os.path.dirname(resized_base))
    except OSError:
        pass
    if ext == '.png' or ext == '.jpg':
        img = None
        for width in RESIZE_WIDTHS:
            img_resized_filename = make_resized_path(resized_base, width, ext)

            if not os.path.exists(img_resized_filename):
                print('Generating %s' % img_resized_filename)

                # Lazy load images
                if img is None:
                    img = Image(filename=path)

                with img.clone() as img_resized:
                    if img.width > width:
                        img_resized.resize(width=width,
                                           height=int(width * (float(img.height) / float(img.width))),
                                           filter='lanczossharp')

                    if ext == '.png':
                        img_resized.format = 'png'
                        img_resized.strip()
                        img_resized.save(filename=img_resized_filename)

                        verbose_flag = '-v' if LOG_VERBOSE else '-q'

                        # Attempt to compress PNG images with pngnq and pngcrush
                        img_nq_filename = make_resized_path(resized_base, width, ext, '_quant')

                        if 99 == subproc(['pngquant', verbose_flag, '-f', '-Q 10-90', '--ext', '_quant.png', img_resized_filename]):
                            print('!!! Quantized PNG quality too low. Using original.')
                            os.rename(img_resized_filename, img_nq_filename)
                        else:
                            os.remove(img_resized_filename)
                        
                        subproc_or_die(['pngcrush', verbose_flag, '-rem alla', '-rem text', img_nq_filename, img_resized_filename])
                        
                        os.remove(img_nq_filename)
                    elif ext == '.jpg':
                        img_resized.format = 'pjpeg'
                        img_resized.compression = 'jpeg'
                        img_resized.compression_quality = 85
                        img_resized.strip()
                        img_resized.save(filename=img_resized_filename)