Is there a way to save snapshots of figures in a LiveScript without keeping the figure objectss open in a for loop?

I have a plotting function in a for loop to go through data and produce a plot for each of them. Let's say the resultant figure contains huge amount of graphic objects, and very heavy in memory.

for i = 1:20
    
    figure
    plot(rand(10,1),rand(10,1))

end

In such cases, it would be useful, if one can keep only the screenshots of figures in a Live Script without keeping the bulky invisible figure objects open.

Hypothetically, if the code below could allow you to save snapshots in a Live Script, without actually keeping the figure object active, that might be convinient. The problem is that the code below will just close all the figures and nothing is shown in a Live Script.

for i = 1:20
    
    figure
    plot(rand(10,1),rand(10,1))

    drawnow
    close
end

This is the closest I could found. Actual plotting is postponed until the for loop finishses. But still the invisible figure objects are accumulating during the for loop.

for i = 1:20
    
    figure
    plot(rand(10,1),rand(10,1))

    drawnow limitrate
    
end

drawnow
close all

Does anyone know to if keeping snapshots in a LiveScript without keeping figure objects is possible?

Answer 1

[Fangjun Jiang]

use saveas() to save the figure image.

test1.mlx, file size is 753k. 20 figures are saved. Each contains individual figure objectives.

for k=1:20
    h=figure;
    plot(rand(3));
end

test2.mlx, file size is 666k. 20 figures are saved but each is an image.

for k=1:20
    h=figure;
    plot(rand(3));
    saveas(h,'test.png');
    imshow('test.png');
end

When your data is really large and complex, maybe the .mlx file with image could be much smaller.

[Kouichi C. Nakamura]

Thanks, but ... you totally missed my point. Question is not about how to save figure by using saveas. Rather, it's about how to save "snapshots" in LiveScripts without keeping figure objects. I want to use LiveScript to keep record of what I'm doing. Probably there is no way...

[Fangjun Jiang]

See update.

[Kouichi C. Nakamura]

Thanks. It took a while to get your idea, but yes, this really works.

Suppose I have hundreds of thousands of objects in each figure, I save them as a small PNG by saveas in each for loop, and immediately use imshow to store those images in the Live Scrpt.

Brilliant, thanks!

Saving an image and reopening it take some overhead.

Although tic-toc measurement is not accurate in LiveScript, it still tells us something.

t1 = zeros
for i = 1:10
    close all
    
    tic
    for k=1:20
        h=figure;
        plot(rand(3));
        
    end
    t1(i) = toc
end

mean(t1)

median(t1)

std(t1)

Elapsed time is 1.11 ± 0.15 seconds (mean ± SD).

clear; close all
tic
for k=1:20
    h=figure;
    plot(rand(3));
    saveas(h,'test.png');
    close(h)
    
    figure
    ax = axes;
    imshow('test.png','Parent',ax);
end
toc

Elapsed time is 45.4 ± 37.0 seconds (mean ± SD).

The overhead time was ~2 seconds per loop.