How to use FFT2

How to apply the 2D FFT functions in Matlab

Description

The note explains in detail how to apply the Matlab 2-dimensional FFT for filtering of two-dimensional signals, e.g. images.
It is shown how to connect the output from fft2 to the actual Fourier transform of the signal, and in particular how transfer functions of simple filters may be coded.

• MATLAB release: MATLAB 7.1.0 (R14SP3)

[urs (us) schwarz]

since this PDF submission does not provide any usable code it should be tagged as a WHITE PAPER
us

[S Mai]

 

[George Caminha]

A good material...

[Vishnuvenkatesh Dhage]

 

[ARJUN KUMAR]

helping material

[HYOJOON CHOI]

good

[asafd asdfasdf]

 

[Vitaly Minchenya]

Very helpful.

[Vitaly Minchenya]

I applied it as follows:

%****FFT Low Pass Filter****%
    %Array dimensions
    M = 1024;
    N = 1024;
    %Sampling intervals
    dx = 1;
    dy = 1;
    %Characteristic wavelengths
    KX0 = (mod(1/2 + (0:(M-1))/M , 1) - 1/2);
    KX1 = KX0 * (2*pi/dx);
    KY0 = (mod(1/2 + (0:(N-1))/N , 1) - 1/2);
    KY1 = KY0 * (2*pi/dx);
    [KX,KY] = meshgrid(KX1,KY1);
    %Filter formulation
    K0 = 0.16;
    T = (KX.*KX + KY.*KY < K0^2);
    %Filter Application
    bwmofilt = ifft2(T.*fft2(bwmo));
    imwrite(bwmofilt,'4.filtered.jpg');
%******END of FFT Low Pass Filter******%

[emine doganay]