Help with imwrite() transparency values

Hello,

Thank you for the help. Im sure this might be an easy fix for someone more advanced with Matlab.

Heres the jist:

I'm saving png files during each iteration of a loop (later I will make the images into a movie). The tricky part is that I'm running this on the cluster at the university, so I can't actually render the figures, which limits my options. As a work around I'm using this code to save the image

      fig=figure('visible','off');

      [code that makes the figure]

      filename = sprintf('/img%d.png', frame) ;
      whereto = [directory filename];
      cdata = zbuffer_cdata(fig)
      imwrite(cdata,whereto);

with

   function cdata = zbuffer_cdata(hfig)
  % Need to have PaperPositionMode be auto
  orig_mode = get(hfig, 'PaperPositionMode');
        set(hfig, 'PaperPositionMode', 'auto');

        cdata = hardcopy(hfig, '-dopengl', '-r96');

        % Restore figure to original state
        set(hfig, 'PaperPositionMode', orig_mode); 
   end

This does almost everything I need it to. It saves the figure as a png and names the files correctly.

The problem is that the figures are a plot of numerous spheres and each sphere has different FaceAlpha and EdgeAlpha values (i'm basically using the sphere() function). When I plot it (locally, where I can actually render the figure) It looks fine and the transparency is correct. However, when I save it like this ALL of the spheres are opaque and have the same transparency.

I think that I'm losing some of the data from the colormap or something, but I'm not sure how to fix it. I can't find this in a forum anywhere either.

Thanks for the help if you can provide it!

David