[PD] Gem: alpha blending without loss of brightness
cyrille henry
cyrille.henry at la-kitchen.fr
Wed Jan 23 18:32:27 CET 2008
hello,
you can set alpha blend type to be the maxinmum of each images.
cyrille
Georg Holzmann a écrit :
> Hallo!
>
> I have again a basic alpha blending problem, where I don't find a solution:
>
> For example I have two images (A + B), which are overlapping at a small
> part (C):
>
> ----------------
> | image A |
> | |
> | |------------------
> | | C | |
> -----------|---- |
> | |
> | image B |
> -------------------
>
> Now I want that image A and image B looks normal (unchanged) and in the
> overlapping part the two images are added so that one sees both - and
> all this with openGL commands (not pix_add or similar, because I have
> lots of such regions).
>
> OK, I gave all images an alpha value of 0.5, but then the whole image
> losses brightness.
>
> So my question: is there a way to get this alpha blending and without a
> loss of brightness in the images ? or can I "renormalize" this effect
> somehow (re-increase the brightness) ?
> (see attached patch where I illustruted this problem with 2 colored
> rectangles)
>
> Thanks for any hint,
> LG
> Georg
>
>
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>
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