How to improve speed when printing multiple images inside a for loop

Question

Mario A 2018-2-1

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回答： Rik 2018-2-2

My code generates a figure on each iteration of a for loop, which is printed to a png file each time. Is there a way to speed up this process by letting Matlab continue with the loop while the printing is ongoing? (like a fork-join kind of flow). Any help will be welcome. Example code:

 for k=1:10
    aux = randn(1e3);
    fh = figure('visible','off'); imagesc(aux);
    print(fh,'-dpng','-r0','./temp.png'); close(fh)
 end

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Rik 2018-2-1

You are overwriting the image on each loop iteration. And have you tried parfor?

Mario A 2018-2-1

The actual code within the for loop (not the example I wrote above) is not compatible with parfor (neither it overwrites the image each time).

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Answer 1

Mario A 2018-2-1

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https://ww2.mathworks.cn/matlabcentral/answers/380292-how-to-improve-speed-when-printing-multiple-images-inside-a-for-loop#answer_303069

在 MATLAB Online 中打开

I just found a solution form the parallel computing toolbox, which is the use of parfeval function. This function allows an asynchronous running of another function. The original example is optimized by writing

 for k=1:10
    aux = randn(1e3);
    fh = figure('visible','off'); imagesc(aux);
    parfeval(@print,0,fh,'-dpng','-r0','./temp.png'); close(fh)
 end

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Answer 2

Rik 2018-2-2

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It is also possible print is inherently slower than it could be, in which case the screencapture FEX submission by Yair Altman might result in a speed increase. You can even use that parfeval in combination with this.