gaussian blur

gaussblur.py

import sys
import os
import math
import Image

def make_filter_kernel(size, sigma_sq):
    s = 0.0
    half = size / 2
    f_min = -(size / 2)
    f_ub = size / 2 + 1
    kernel = [[0 for x in range(size)] for y in range(size)]
    for y in range(f_min, f_ub):
        for x in range(f_min, f_ub):
            w = math.exp(-(x * x + y * y) / (2.0 * sigma_sq))
            kernel[half + y][half + x] = w
            s += w
    for y in range(size):
        for x in range(size):
            kernel[y][x] /= s
    return kernel

def render_filter_kernel(kernel, size):
    im = Image.new('L', (size, size), 0)
    max_val = max([max(l) for l in kernel])
    buf = im.load()
    for y in range(size):
        for x in range(size):
            buf[x, y] = 255.0 * kernel[y][x] / max_val
    im.save('kernel.png')

def blur_image(im, filter_size, sigma_sq):
    filter_mergin = filter_size / 2
    reduce_size = (-2 * filter_mergin, -2 * filter_mergin)
    new_size = map(sum, zip(im.size, reduce_size)) 
    new_im = Image.new('RGBA', new_size, 0x00000000)
    kernel = make_filter_kernel(filter_size, sigma_sq)
    render_filter_kernel(kernel, filter_size)
    src = im.load()
    dst = new_im.load()
    for y in range(new_size[1]):
        for x in range(new_size[0]):
            r, g, b = (0.0, 0.0, 0.0)
            for fy in range(filter_size):
                for fx in range(filter_size):
                    w = kernel[fy][fx]
                    sr, sg, sb, sa = src[x + fx, y + fy]
                    r += w * sr
                    g += w * sg
                    b += w * sb
            dst[x,y] = (sa<<24) | (int(b)<<16) | (int(g)<<8) | (int(r)<<0)
            print '\033[2K\033[30D%3.2f percent processed'%(float(y * new_size[1] + x) * 100 / (new_size[0] * new_size[1])),
            sys.stdout.flush()
    return new_im

if __name__ == '__main__':
    if len(sys.argv) < 2:
        sys.stderr.write('filename please!\n')
        sys.exit(1)
    filename = sys.argv[1]
    im = Image.open(filename).convert('RGBA')
    im = blur_image(im, 15, 15.0)
    root, ext = os.path.splitext(filename)
    im.save(root + '_blur' + ext)