Transperancy when drawing to bitmap


I am rendering to a bitmap, the way it is explained in the opengl superbible (p.599).

But I am loosing tranperancy information of bitmaps that I blit onto the viewport. Can someone give me a hint what I have to change in the example of the book, that I can render transperant bitmaps into a bitmap?

thanks a lot

AFAIK it’s not possible to store transparency information into a bitmap, you should choose for a file type as 32 bits TGA.

Nate has a good TGA reading/writing OpenGl library:

Hope this helps,

Daniel Palomo van Es