Thread Subject: How to set 'white' color to be transparent to its background?

Dear all
These days, I use GUIDE to create a toolbar in a GUI application. Each
tool in this toolbar was set to an icon picture. An difficult problem
was encountered, that is: there are many white color space in the
icon, so it looks not very beautiful. I want to set 'white' icon as a
transparent color to the toolbar background , how to get that? Below
is my code, I hope you can help me to resolve this problem.

[I1, Map] = imread(utt_Icon); % utt_icon is 'png' format picture
file.
set(hObject, 'CData', ind2rgb(I1, Map));


Best Regards
mayi
2009-8-11