Rasterized PDF output after manually setting 'FaceVertexCData' of a patch in MATLAB - matlab

Question

I'm running into a problem trying to produce vector PDF plots after manually setting colors of patches.
After setting the colors of patch faces and vertices using a call to set(...) to set the 'FaceVertexCData' property of a patch, the PDF output produced by both 'savefig' and 'saveas' is rasterized and no longer in vector format. This does not occur when 'FaceVertexCData' is not altered.
For example,
clear all; close all;
h = bar([1 2 3 ; 3 2 1 ; 3 4 4]);
saveas(gcf, 'barplot.pdf', 'pdf');
savefig('barplot.pdf', 'pdf');
produces a perfectly fine vectorized PDF of the plots.
On the other hand, the following code will produce ugly vectorized PDF plots:
clear all; close all;
h = bar([1 2 3 ; 3 2 1 ; 3 4 4]);
ch = get(h,'children');
set(ch{1},'FaceVertexCData',[1 0 0 ; 0 1 0; 0 0 1]);
set(ch{2},'FaceVertexCData',[1 0 0 ; 0 1 0; 0 0 1]);
set(ch{3},'FaceVertexCData',[1 0 0 ; 0 1 0; 0 0 1]);
saveas(gcf, 'barplot_savefig_FaceVertexCData.pdf', 'pdf');
savefig('barplot_saveas_FaceVertexCData.pdf', 'pdf');
What is the cause of the problem? How can this be resolved? Any hints will be welcome.
Thanks much.
Edit: MATLAB Version: 8.0.0.783 (R2012b) on OS X

Answer 1

I have solved the problem.
For posterity:
The workaround for this is to not specify RGB colors directly, but define them in a color map, which is then indexed.
The following code will solve the problem:
clear all; close all;
% Make the bar plot
h = bar([1 2 3 ; 3 2 1 ; 3 4 4]);
ch = get(h,'children');
% Define the colors in a color map
cMap = [1 0 0 ; 0 1 0; 0 0 1];
colormap(cMap);
% Now set the FaceVertexCData by indexing into the colormap
set(ch{1},'CDataMapping', 'direct', 'FaceVertexCData',[1 2 3]');
set(ch{2},'CDataMapping', 'direct', 'FaceVertexCData',[1 2 3]');
set(ch{3},'CDataMapping', 'direct', 'FaceVertexCData',[1 2 3]');
% Save out, this will produce vectorized PDF
saveas(gcf, 'barplot_savefig_FaceVertexCData.pdf', 'pdf');
savefig('barplot_saveas_FaceVertexCData.pdf', 'pdf');
The following piece of information about this is relevant:
"RGB color data not yet supported in Painter's mode - you will see this as a warning if you try to export a figure which contains patch objects whose face or vertex colors are specified as a an RGB colour, rather than an index into the colormap, using the painters renderer (the default renderer for vector output). This problem can arise if you use pcolor, for example. This is a problem with MATLAB's painters renderer, which also affects print; there is currently no fix available in export_fig (other than to export to bitmap). The suggested workaround is to avoid colouring patches using RGB. First, try to use colours in the figure's colourmap - change the colourmap, if necessary. If you are using pcolor, try using uimagesc (on the file exchange) instead."
(https://sites.google.com/site/oliverwoodford/software/export_fig, accessed June 11, 2013).