This article was contributed by Jason Wylie . This code makes use of some code from Zafir Anjum, specifically the code to load a background image.
Every window has a Region.
This is how Windows knows what area of the screen to draw on when something changes in your program. What I have done is scan through the window pixel by pixel looking for the color I want to make transparent. I find that color, I add it to a temporary Region. I collect all the transparent spaces, then invert it and assign it to the window. The CRgn class, as it turns out, it a very powerful little class.