CODEWITHSUNDEEP
imagematlabfiltering
user3524911
user3524911

Reputation: 13

MATLAB fourier image filtering

I am currently learning how to filter images using Fourier transform in Matlab. I managed to apply a low pass filter on an image, the problem is, I cannot do the same with high pass filter. Here are codes and images that I got. Could you help me?

clc

clear

A=imread('3.tif'); % image size is 200 x 200

B=fftshift(fft2(A));

mask=zeros(200);

mask(80:120,80:120)=1;

C=mask.*B;

D=ifft2(C);

D=uint8(D);

imshow(D);

Here the results:

https://i.sstatic.net/Y2UaI.png

The problem occures when I try to apply an inverse mask, like so:

clc

clear

A=imread('3.tif'); % image size is 200 x 200

B=fftshift(fft2(A));

mask=zeros(200);

mask=mask+255;

mask(80:120,80:120)=0;

C=mask.*B;

D=ifft2(C);

D=uint8(D);

imshow(D);

Results:

https://i.sstatic.net/NzYNG.png

What is wrong?

Upvotes: 1

Views: 5476

Answers (1)

Rafael Monteiro
Rafael Monteiro

Reputation: 4549

Change this on the second code:

mask=zeros(200);
mask=mask+255;

... to this

mask=ones(200);

You also forgot to call ifftshift on both codes:

D=ifft2(ifftshift(C));

Here is what I got:

  • Lowpass:

enter image description here

  • Highpass:

enter image description here

Upvotes: 3

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