What does this mean in MATLAB?

Question

I have came about a MATLAB code like the following:

xyz = imfilter(A,B);
xyz_subsample = xyz(1:2:size(xyz, 1), 1:2:size(xyz, 2));

The code is related to subsampling. But, what does the second line mean?

Thanks.

score 4 · Accepted Answer · answered Nov 10 '13 at 13:41

4

The second line is taking every second sample in each spatial dimension. So it's downsampling by a factor of 2 in each dimension.

Downsampling should be preceded by lowpass filter in order to avoid aliasing effects. The filter in the first line probably does that. Is B a lowpass mask?

answered Nov 10 '13 at 13:41

Luis Mendo

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Thanks for your answer. Yes, `B` is a lowpass filter – Simplicity Nov 10 '13 at 18:30

score 2 · Answer 2 · answered Nov 10 '13 at 13:24

2

The second line uses the colon operator to select every second row and every second colum, which means that every 4th pixel is selected.

answered Nov 10 '13 at 13:24

Daniel

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What does this mean in MATLAB?

2 Answers2