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Re: [pygame] SDL vs. Pygame: Alpha Differences

To: pygame-users@xxxxxxxx
Subject: Re: [pygame] SDL vs. Pygame: Alpha Differences
From: Pete Shinners <pete@xxxxxxxxxxxx>
Date: Sat, 23 Dec 2006 16:50:36 -0800
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In-reply-to: <458D8D51.9000106@kamilche.com>
References: <458D8D51.9000106@kamilche.com>
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On Sat, 2006-12-23 at 12:10 -0800, Kamilche wrote:
> In the SDL documentation, it says under 'SDL_SetAlpha':
> 
> "When blitting RGBA->RGBA with SDL_SRCALPHA: The source is alpha-blended 
> with the destination using the source alpha channel. The alpha channel 
> in the destination surface is left untouched. SDL_SRCCOLORKEY is ignored."
> 
> However, in Pygame, the alpha channel IS overwritten. Is there any 
> technique to overcome this, to make it match what is written in the SDL 
> documentation? Or is it a bug in SDL?

Yes, SDL has a special blitter for blending alpha to alpha. You can work
around this by disabling the SRC_ALPHA flag on the source. then it will
work the same as SDL.

Follow-Ups:
- Re: [pygame] SDL vs. Pygame: Alpha Differences
  - From: Brian Fisher
- Re: [pygame] SDL vs. Pygame: Alpha Differences
  - From: Kamilche

References:
- [pygame] SDL vs. Pygame: Alpha Differences
  - From: Kamilche

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