How to grab the backbuffer with alpha

BlitzMax Forums/BlitzMax Programming/How to grab the backbuffer *with* alpha

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EPS

Here my method:

Render the Backbuffer twice. First on $FFFFFF (white) as Background Color and then on $000000 (black) as Background Color. Grab both rendered images and with that you can calculate the Alpha Transparency into a third Image/Buffer.

Not really fast - but possible.

sorry for my bad english...