Creation of an Ideal Lowpass filter.

Question

Tim van Schaik 2021-5-4

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/821695-creation-of-an-ideal-lowpass-filter

回答： Tim van Schaik 2021-5-4

So for an exercise where you have to create an ideal filter an example was given to start you up, the problem with this exercise is that the creation of this filter almost seems impossible. First I will display the code

PQ=2*size(MRI);

[U,V]=dftuv(PQ(1),PQ(2));

D=sqrt(U.^2+V.^2);

D0=0.05*PQ(2);

F=fft2(MRI,PQ(1),PQ(2));

HidealH=piecewise(D<=D0,1,D>D0,0)

Here is the function dftuv given by.

function [U, V]=dftuv(M,N);

u=0:(M-1); v=0:(N-1);

idx=find(u>M/2); u(idx)=u(idx)-M;

idy=find(v>N/2); v(idy)=v(idy)-N;

[U, V]=meshgrid(v,u);

end

The problem lies in the HidealH part as that does not seem to work,nor I have no clue how to fix it. You are comparing D0 which is just a single value to D which is a matrix of MxN size, the piecewise function does not work here and I have no clue how to fix it so that for values of D<=D0 it becomes 1 and else it become 0.

If somebody could point me in the right direction I would be eternally gratefull.