How do I change a 512*512 image code to any size code?
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Diptayan Dasgupta
on 12 May 2021
Commented: Diptayan Dasgupta
on 13 May 2021
I wrote the code to find the lowpass filter of grayscale image of size 512*512 pixels. How to change it to any other size?
A=imread('lena.png'); % read 512512 8bit image
A=double(A);
A=A/255;
SP=fftshift(fft2(fftshift(A)));
D=abs(SP);
D=D(129:384,129:384);
figure;imshow(A);
title('Original image')
figure;imshow(30.*mat2gray(D)); % spectrum
title('Original spectrum')
c=1:512;
r=1:512;
[C, R]=meshgrid(c, r);
CI=((R-257).^2+(C-257).^2);
filter=zeros(512,512);
% produce a high-pass filter
for a=1:512;
for b=1:512;
if CI(a,b)>=20^2; %filter diameter
filter(a,b)=0;
else
filter(a,b)=1;
end
end
end
G=abs(filter.*SP);
G=G(129:384,129:384);
figure;imshow(30.*mat2gray(G));
title('Low-pass spectrum')
SPF=SP.*filter;
E=abs(fftshift(ifft2(fftshift(SPF))));
figure;imshow(mat2gray(E));
title('Low-pass image')
1 Comment
Walter Roberson
on 12 May 2021
You did not post the code, so we do not know what implementation you used.
Accepted Answer
DGM
on 13 May 2021
This should be a start
% this presumes the image is uint8, so be careful
% if you have IPT, you can use im2double() instead
A=double(A);
A=A/255;
% ...
% these numbers in the following rows are functions
% of the presumed image geometry and/or the size of the filter
% rewrite them in general terms; for example:
% [h w nc] = size(A);
% padsize = floor([h w]/4); % assuming the same ratio
% D = D((1+padsize):(h-padsize),(1+padsize):(w-padsize));
D=D(129:384,129:384);
% ...
c=1:512; % 1:w
r=1:512; % 1:h
% ...
CI=((R-257).^2+(C-257).^2); % 257 is ((h or w)/2 + 1)
filter=zeros(512,512); % filter=zeros(h,w);
for a=1:512 % 1:h
for b=1:512 % 1:w
% maybe filter diameter should be defined earlier as a parameter
if CI(a,b)>=20^2
% ...
end
end
end
% ...
G=G(129:384,129:384); % etc
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