problem on drawing theme background on a bitmap

[Li kai Liu Angus]

Hi, Just wondered if anyone has tried this already? I'm trying to write a button control that use APIs in uxtheme.dll to draw its background image. I also want to have an alpha blend option for the button. My solution is to draw the theme background on a temporary bitmap, do the alpha blending, and then, copy it to the screen. But here comes a problem. If theme background already contains some pixels which are semi-transparent, these pixels are drawn in black color on the target bitmap. While there isn't any problem if I want the theme background image to be drawn on the screen (alpha pixels are rendered correctly on the screen, perfectly drawn on top of whatever sits there.) Does anyone know the solution to draw a theme background correctly onto a bitmap? Thanks:) Li-kai Liu