matlabuser-interfaceexportui-automationundocumented-behavior

Exporting figures programmatically (R2019a)

In MATLAB R2019a a new way to export figures was added whereby the result "is tightly cropped around the axes with minimal white space". This feature is accessed using the axes toolbar:

enter image description here

My question is: How do we invoke this new export feature programmatically?

It should be fairly easy to get the export dialog to open for specific axes (i.e. simulate a button click), but I'm more interested in bypassing the dialog and just saving a file to disk, e.g.

croppedExport(hAxes, outputPath);


P.S.
I am aware that this functionality can be achieved using a 3rd party tool like export_fig.

Solution

  • TL;DR

    matlab.graphics.internal.export.exportTo(hAxes, fullpath);

    The tooltip of this new button says "Export...", which is going to help us identify it. Digging within the properties of the axes toolbar (struct(hAxes.Toolbar)) we can get a glimpse of the function that is being called when the button is pressed:

    hB = struct(struct(hAxes.Toolbar).ButtonGroup).NodeChildren(1);
%{
hB = 
  ToolbarPushButton (Export...) with properties:

            Tooltip: 'Export...'
               Icon: 'export'
    ButtonPushedFcn: @(e,d)matlab.graphics.internal.export.exportCallback(d.Axes)
%}

    which unfortunately points to directory full of .p files:

    ...\MATLAB\R2019a\toolbox\matlab\graphics\+matlab\+graphics\+internal\+export

    ...and forces us to do proceed with trial and error. For example, we can choose a random .p file whose name sounds right to us, and see if we can discover its API:

    >> matlab.graphics.internal.export.exportTo()
Error using matlab.graphics.internal.export.exportTo
Not enough input arguments. 

>> matlab.graphics.internal.export.exportTo('')
Error using matlab.graphics.internal.export.exportTo
Not enough input arguments. 

>> matlab.graphics.internal.export.exportTo('','')
Error using matlab.graphics.internal.export.ExporterArgumentParser/parseInputParams
'' matches multiple parameter names: 'background', 'destination', 'format', 'handle', 'margins', 'resolution', 'target'. To avoid ambiguity, specify the complete name of the parameter.
Error in matlab.graphics.internal.export.ExporterArgumentParser/processArguments
Error in matlab.graphics.internal.export.Exporter/process
Error in matlab.graphics.internal.export.exportTo

    The last error message provides very interesting information, which allows us to take some educated guesses regarding the required inputs:

    'background'  - probably background color
'destination' - probably where to put the file
'format'      - probably what is the file extension
'handle'      - probably the axes handle
'margins'     - (self explanatory)
'resolution'  - (self explanatory)
'target'      - ???

    Following the "minimal" input set that is requested in the question, our next attempt is:

    membrane;
matlab.graphics.internal.export.exportTo('handle', gca, 'destination', 'e:\blabla.png');

    ... which creates the a file at the desired location and also returns a truecolor RGB image that is cropped just like we wanted!

    enter image description here

    Although we are done, we can try to simplify this function call even further based on the "convention" of saveas, which is saveas(what, where, ...):

    matlab.graphics.internal.export.exportTo(gca, 'e:\blabla.png');

    ... which works (!) and so this becomes our method of choice.