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<RTE_TEXT>Is it possible to set the alpha transparency on an existing color within a surface, and cause that color & anything beneath it to have 0 alpha, completely transparent???<BR>
<BR>
example:<BR>
I want to draw a purple rectangle on a surface, over existing image data.<BR>
Next, I want to make that rectangle completely transparent in the resulting png file (i.e., 'set any/all areas that are purple to 100% transparent on cairo_surface_t *surface'). I dont want any existing colors/graphics that were below the rectangle to show up.<BR>
<BR>
I tried using "set_source_rgba" and setting the alpha to '0.0', but this doesnt cause the underlying colors/images to become transparent...<BR>
<BR>
How can I achieve this effect? similar to gd's "gdImageColorTransparent" function...<BR>
Please help...<BR>
Thanks,<BR>
P.Romero<BR>
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