drop shadow using scaled rectangles.corner area representation is poor.

dropshadow2.py

import sys
import os
import math
import Image

def create_shadow_image(image_size, shadow_size):
    mergin = (shadow_size, shadow_size)
    new_size = map(sum, zip(image_size, mergin, mergin))
    im = Image.new('RGBA', new_size, 0xFFFFFFFF)
    buf = im.load()
    for i in range(1, shadow_size + 1):
        offset = shadow_size - i
        for y in range(image_size[1] + i * 2):
            for x in range(image_size[0] + i * 2):
                r, g, b, a = buf[x + offset, y + offset]
                r = max(r - 0x08, 0)
                g = max(g - 0x08, 0)
                b = max(b - 0x08, 0)
                buf[x + offset, y + offset] = (r, g, b, a)
        print '\033[2K\033[30D%3.2f percent processed'%(float(i) * 100 / (shadow_size)),
        sys.stdout.flush()
    return im

def draw_shadowed_image(filename):
    SHADOW_SIZE = 15
    im = Image.open(filename)
    new_im = create_shadow_image(im.size, SHADOW_SIZE)
    offset = (SHADOW_SIZE,) * 4
    base = (0, 0) + im.size
    new_im.paste(im, map(sum, zip(base, offset)))
    root, ext = os.path.splitext(filename)
    new_im.save(root + '_shadowed' + ext)

if __name__ == '__main__':
    if len(sys.argv) < 2:
        sys.stderr.write('filename please!\n')
        sys.exit(1)
    draw_shadowed_image(sys.argv[1])