how i can do sub-sampling for an image with factor 4
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to perform sub-sampling using matlab
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Accepted Answer
Youssef Khmou
on 26 Feb 2013
Edited: Youssef Khmou
on 26 Feb 2013
hi ,
you can use the function " downsample" twice ,
example :
I=imread('circuit.tif');
J=downsample(I,4);
J=downsample(J',4)';
whos I J
imshow(J)
figure, imshow(I)
Size(I)= 4² * Size(J) .
2 Comments
Wayne King
on 26 Feb 2013
Edited: Wayne King
on 26 Feb 2013
keep in mind that downsample() in the Signal Processing Toolbox only downsamples the matrix along the row dimension.
More Answers (1)
Wayne King
on 26 Feb 2013
Do you want to downsample along the row dimension, along the column dimension, or both?
X = randn(24,24);
% Along row only
Im = X(1:4:end,:);
% Along column dim only
Im = X(:,1:4:end);
% Along both
Im = X(1:4:end,1:4:end);
Keep in mind that the above gives only one "phase" of the downsampling. When downsampling by M, there are M such phases. To see an illustration of this for a 1-D signal, see
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