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I tried to padarray more than 1000 images. However when I time my code, this specific line take the highest amount of time to complete

I=abs(padarray(I, [2, 2], 'replicate', 'both'));

Mainly because of the line 35 of the padarray algorithm (inside profiler): images\private\padarray_algo

b = a(aIdx{:});

Any way to improve the efficiency? Perhaps using another method? Thanks!

Gregor Isack
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1 Answers1

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You can use repmat and matrix concatenation to get the same result:

r=@repmat;
pad=@(I,d)[r(I(1),d)    r(I(1,:),d(1),1)   r(I(1,end),d)
       r(I(:,1),1,d(2)) I                  r(I(:,end),1,d(2))
       r(I(end,1),d)    r(I(end,:),d(1),1) r(I(end),d)];

Usage:

pad(I,[2 2])

If all images are of the same size you can create a matrix of linear indices of the image and apply padarray to it then use padded index array to pad images:

%create matrix of indices
Idx = reshape(1:numel(I),size(I));
%pad the index
Idx_padded = padarray(Idx, [2, 2], 'replicate', 'both'); 
%use the padded index to pad images
result = I(Idx_padded);
result2 = I2(Idx_padded);
rahnema1
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    First method more or less the less since multiple calling of function. However that second method is genius! It saved me days of computation. Thank you so much! – Gregor Isack May 24 '17 at 09:06