Error using 'getframe' in an embedded Matlab function in a Simulink Model

I am trying to use 'getframe' in a Matlab function within a Simulink Model. I get the error "Cannot get field colormap from struct colormap. Block Baseband Waterfall Spectrum/MATLAB Function1 (#74) While executing: none "

Now, obviously the 'colormap' field is empty. For some reason when you use 'getframe' within Simulink it is unable to deal with an empty field. Seams to work fine in Matlab. So is this a bug? Is there a way around the problem?

Please see the function code below:

function mycdata  = fcn(v,Myhandle0,count)%#codegen

coder.extrinsic('get'); 
coder.extrinsic('subplot');
coder.extrinsic('getframe');
mymovie = struct('cdata',uint8(zeros(420,560,3)),'colormap',double([]));

figure1 = Myhandle0;

if count >0
    subplot2 = subplot(1,2,2,'Parent',figure1);
    surf(v,'Parent',subplot2,'LineStyle','none');
    mymovie =getframe(figure1);
    mycdata = mymovie.cdata;
    hold off;
else
    mycdata = uint8(zeros(420,560,3));
end

end

[Walter Roberson]

It probably will not make any difference, but the official syntax for the struct in MATLAB would be

mymovie = struct('cdata', {uint8(zeros(420,560,3))}, 'colormap', {double([])});

and you could probably use zeros(0,0) instead of double([])

Answer 1

[Fred Smith]

I think this is a bug or a limitation depending on what version you are using. Prior to R2012b, empty-fields were not supported by MATLAB Function blocks.

Functionality very similar to this worked fine for me in the latest development version.

What version of MATLAB are you using?

[Chris]

I am using R2012b (8.0.0.783) linux 64bit, August 22, 2012.

[Tong Zhao]

I just got myself into similar situations, it seems not easy to get getframe() to work within a MATLAB function block. Some examples would be great.