blur .jpg image

hello,
i am a beginner in programming with matlab and i am using the
psychotoolbox oneself for the first time.

i have just question on blurring images in jpg-format. as i am a
beginner my qusestions are very basic.

first i displayed an .jpg image using the following programm:

function ShowImage3

screenNum=0;
res=[1280 1024];
clrdepth=32;
[wPtr, rect]=Screen('OpenWindow', screenNum, 0, [0 0 res(1) res(2)],
clrdepth);

img = imread ('Face2', 'JPG');
textureIndex=Screen('MakeTexture', wPtr, double(img));
Screen('DrawTexture', wPtr, textureIndex);
Screen(wPtr, 'Flip');

WaitSecs(8);


Displaying the image works. but i have real problems to blur is.
i found the following proposal in the psychtoolbox forum:

Image=imread('');

rAng=angle(fft2(randn(size(Image))));
Noise1=real(ifft2(abs(fft2(Image)).*(cos(rAng)+sin(rAng).*i)));

how can i implement it?

best wishes

bernadette