Perform distributed image processing, such as resizing, using an IPython cluster

parallel_process_images.py

# Start a basic, 4 node, local, ipython cluster, using:
#   ipcluster start -n 4
#
# then run:
#   ipython parallel_process_images.py
#

# this example reads in ./test_images/*.jpg
# and outputs a bunch of .png files to ./resized_test_images/

from IPython.parallel import require
from IPython.parallel import Client

def run():

    files = [f for f in glob.glob('./test_images/*.jpg') if 'palette' not in f]

    client = Client()
    
    view = client.load_balanced_view()
    async_results = []
    
    for f in files:
        ar = view.apply_async(
            process_image, 
            f,
            save_to_dir="./resized_test_images"
            )

        async_results.append(ar)

    print("Submitted tasks: ", len(async_results))
    client.wait(async_results)

    for ar in async_results:
        print ar.display_outputs()


def process_image(file, save_to_dir):    
    import png_image_set # requires png_image_set.py

    print "processing %s" % file
    p = png_image_set.PngImageSet()
    p.make_png_imageset(file, save_to_dir=save_to_dir)


if __name__ == '__main__':
    run()

png_image_set.py

import os
import glob   
from PIL import Image, ImageOps, ImageChops 

class PngImageSet(object):    
    '''
    Resizes images by re-fitting them into a given size, 
    pads with white background and maintains aspect ratio.

    If no save_to_dir is specified, then dir of original
    image is used.

    Adds width to filename.
    eg: 
        somepicture.jpg => somepicture.160.png
    '''
    def make_png_imageset(
        self,
        file, 
        save_to_dir=None, 
        sizes=[(80,80), (160, 160), (240,240), (320,320), (640,640)],
        quality=85
        ):
        
        file = os.path.abspath(file)

        file_dir = os.path.dirname(file)        
        file_noext, file_ext = os.path.splitext(file)
        file_noext = os.path.basename(file_noext)

        if save_to_dir is not None:
            save_to_dir = os.path.abspath(save_to_dir)
        else:
            save_to_dir = file_dir        

        image = Image.open(file)   

        for size in sizes:
            new_image_file = os.path.join(save_to_dir, file_noext + '.' + str(size[0]) + '.png')

            new_image = image.copy()
            
            new_image.thumbnail(size, Image.ANTIALIAS)

            offset_x = max( (size[0] - new_image.size[0]) / 2, 0 )
            offset_y = max( (size[1] - new_image.size[1]) / 2, 0 )        

            thumb = Image.new(mode='RGBA',size=size, color=(255,255,255,255))         
            thumb.paste(new_image, (offset_x, offset_y))        
            thumb.save(new_image_file, 'PNG', quality=quality)