getframe() captures the wrong part of the screen when figure is maximized (R2021b)

I want to save full-screen images (or as large as I can make them) containing only what's plotted in the axes. To do this, I create a maximized figure and then use getframe(ax) to capture the axes. This used to work in previous versions of Matlab but I haven't tried it with any version between R2015b and R2021b.

Here is a minimum working example:

% Make dummy data to plot
x = linspace(0, 2*pi, 20);
y = sin(x);

% Make figure and axes:
f1 = figure(1);
f1.WindowState = 'maximized';
ax1 = axes('Parent', f1);
plot(ax1, x, y)

% Save an image of what's on the axes:
frame = getframe(ax1);
imwrite(frame.cdata, 'example.png')

Attached is the image that gets saved as a result. It is improperly cropped around the bottom left part of the axes and contains parts outside the axes. I have also tried adding a pause(1.0) command before calling getframe() but it produces the same image. The behavior is the same if I call getframe() without arguments and let it choose the current axes. However, when the figure is not maximized, the saved image does indeed contain only what is in the axes.

How can I capture the axes properly when the parent figure is maximized?

[Walter Roberson]

Have you experimented with exportgraphics() ?

[Nathan]

exportgraphics() seems to work much better. Thanks for the suggestion!

Just to document what I'm changing: exportgraphics() captures the axis tick labels by default, but I discovered I can turn them off by setting:

ax1.XTick = [];
ax1.YTick = [];

I don't need a grid, but if a grid is desired in the plot, one could substitute these commands instead:

ax1.XTickLabels = [];
ax1.YTickLabels = [];

Then I create the image with:

exportgraphics(ax1, 'example2.png');

Answer 1

[Image Analyst]

This works fine for me:

% Make dummy data to plot
x = linspace(0, 2*pi, 20);
y = sin(x);
% Make figure and axes:
f1 = figure(1);
f1.WindowState = 'maximized';
ax1 = axes('Parent', f1);
plot(ax1, x, y)
drawnow;
% Save an image of what's on the axes:
exportgraphics(ax1, 'example.png')

Your original code only saved stuff inside the box, not the tick labels, like this code does.

[Nathan]

Thanks for your response. When I run that code, I get the tick labels in my saved image (I attached it). Are there settings I should change or something?

[Image Analyst]

Yep, that's what I get. Is there a problem with it? Do you not want labels? Your original code did not have labels, so if you don't want tick labels you can use that code. There are lots of settings you can change but you have to say what you want. Right now you have two programs, one to give you labels and one that does not. What else do you want or not want?

[Nathan]

Oh, no I think I just misunderstood your comment. I thought you expected your code to make an image without tick labels. There's no problem with that result.

[Image Analyst]

Nathan, see attached demo to see how you can change almost everything on the axes.

[Nathan]

Regarding the exportgraphics() workaround, I also want to be able to make animations with a videowriter. I suppose I can save an image to disk, then load it back into the workspace, and save it as a frame in a video object, but that seems inefficient and I expect it to be much slower. Is there a way to keep the captured image in the Matlab workspace, or is getframe() the only function that does this?

[Walter Roberson]

Perhaps some method could be found using copygraphics(), which copies to the system clipboard? At the moment I do not know how to retrieve from the system clipboard.

[Nathan]

It looks like this should work but I haven't tried it yet. Maybe I'll tinker tomorrow:

https://www.mathworks.com/help/matlab/ref/clipboard.html#d123e182981

I'm pretty sure the strange cropping from getframe() is not the intended behavior but I'm not sure if I've done something wrong or if it's a bug. Should I submit a bug report?

[Image Analyst]

Sure, if you want to.

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