pixelLabelDatastore read() function gets progressively slower

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Louis Vaickus
Louis Vaickus 2018-5-1
回答： Louis Vaickus 2018-5-4
The following code proceeds quickly (200 images/sec) until around the 12,000th read at which point the read time increases by roughly 10% per 200 reads flattening out at about 20 images/sec.
There are 1.4x10^6 images in the directory.
At the initial rate of 200/sec execution would take 2 hours to complete.
At the rate read settles to it would take 20 hours.
pxds = pixelLabelDatastore('directory', classes, LabelIDs);
parfor r = 1:length(pxds.Files);
img_holder{r} = uint8(ones(200,200));
end
counter = 1;
while hasdata(pxds);
img_holder{counter} = uint8(read(pxds));
counter = counter + 1;
end

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采纳的回答

Louis Vaickus
Louis Vaickus 2018-5-4
I ended up making an imagedatastore of the labelled images and then creating the categorical images and imwrite()'ing them in a parfor loop. It progressed at 500 images per second and did not slow down.
function y = convert_categorical(imds);
parfor r = 1:length(imds.Files);
[img, info] = imds.readimage(r);
[~, filename, ext] = fileparts(info.Filename);
if exist([path filename ext], 'file') == 0;
q = uint8(ones(227,227));
q(img(:,:,1) == 0 & img(:,:,2) == 0 & img(:,:,3) == 255) = 1;
q(img(:,:,1) == 255 & img(:,:,2) == 255 & img(:,:,3) == 255) = 2;
q(img(:,:,1) == 0 & img(:,:,2) == 255 & img(:,:,3) == 0) = 3;
imwrite(q,[path filename ext]);
end
end
end

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