gaussian_filter.py

from __future__ import division
from numpy import array, zeros, abs
from numpy.fft import fft2, ifft2
from PIL import Image
from matplotlib.pyplot import imshow, show, subplot, figure, gray, title, axis

def gaussian(im):
    b = array([[2, 4,  5,  2,  2],
               [4, 9,  12, 9,  4],
               [5, 12, 15, 12, 5],
               [4, 9,  12, 9,  4],
               [2, 4,  5,  4,  2]]) / 156;
    kernel = zeros(im.shape)
    kernel[:b.shape[0], :b.shape[1]] = b

    fim = fft2(im)
    fkernel = fft2(kernel)
    fil_im = ifft2(fim * fkernel)

    return abs(fil_im).astype(int)

if __name__ == "__main__":
    from sys import argv
    if len(argv) < 2:
        print "Usage: python %s <image>" % argv[0]
        exit()
    im = array(Image.open(argv[1]))
    im = im[:, :, 0]
    gray()

    subplot(1, 2, 1)
    imshow(im)
    axis('off')
    title('Original')

    subplot(1, 2, 2)
    imshow(gaussian(im))
    axis('off')
    title('Filtered')

    show()