scale.py

import PIL
import numpy

def scale(image, max_size, method=PIL.Image.ANTIALIAS):
    """
    resize 'image' to 'max_size' keeping the aspect ratio
    and place it in center of a noisy 'max_size' image
    """
    im_aspect = float(image.size[0])/float(image.size[1])
    out_aspect = float(max_size[0])/float(max_size[1])
    if im_aspect >= out_aspect:
        scaled = image.resize((max_size[0], int((float(max_size[0])/im_aspect) + 0.5)), method)
    else:
        scaled = image.resize((int((float(max_size[1])*im_aspect) + 0.5), max_size[1]), method)

    offset = (((max_size[0] - scaled.size[0]) / 2), ((max_size[1] - scaled.size[1]) / 2))
    imarray = numpy.random.rand(max_size[0], max_size[1], 3) * 256
    back = PIL.Image.fromarray(imarray.astype('uint8')).convert('RGB')
    back.paste(scaled, offset)
    return back