[Mono-dev] Bitmap manipulation - am I doing it right?

Stifu stifu at free.fr
Wed Apr 1 06:20:45 EDT 2009

I just read a bit on this, and it sounds just like what I need. :)

StApostol wrote:
> Την Wed, 01 Apr 2009 09:08:02 +0300,ο(η) Stifu <stifu at free.fr> έγραψε:
>> How would that layer on top work, technically?
>> Because if it's not part of the same Bitmap (the only painted on the  
>> Panel)
>> and I that I need to paint twice, then there's some flickering happening.
>> Hence the need for double buffering.
> I cannot speak for GDI+, because I don't know its architecture. However it  
> does support alpha channels, which means it should be able to do alpha  
> blending. An easy test is to render a filled rectangle with A = 128, using  
> the Graphics object of the panel. (Hook the Paint event and make sure the  
> Bitmap is rendered before the Rectangle.)
> If you are using double-buffering, the composition will always happen in  
> the backbuffer - hence no flickering.
> Some general reading on alpha blending:
> http://en.wikipedia.org/wiki/Alpha_compositing
> Code project article on alpha blending Bitmaps (which is not what you  
> actually want, but may be useful if the above technique does not work):
> http://www.codeproject.com/KB/GDI-plus/AlphaBlending.aspx
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