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Bug 2009 - Bug Alpha + ColorKey + 32 bpp
Summary: Bug Alpha + ColorKey + 32 bpp
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: *don't know* (show other bugs)
Version: HG 2.0
Hardware: x86_64 Linux
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords: target-2.0.0
Depends on:
Blocks:
 
Reported: 2013-08-04 16:20 UTC by Sylvain
Modified: 2013-08-08 05:35 UTC (History)
0 users

See Also:

Attachments
sample program (1.94 KB, text/x-csrc)
2013-08-04 16:20 UTC, Sylvain 		Details
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Description Sylvain 2013-08-04 16:20:56 UTC 
Created attachment 1270 [details]
sample program

Hi,

A texture is creating from a 32BPP surface having both Alpha-per-surface + ColorKey. Colorkey seems not to work because the pink color key actually appears when the texture is rendered.

Using 16BPP would solve the issue.

see attached sample program.

thanks,

Sylvain
Comment 1 Sam Lantinga 2013-08-04 23:38:41 UTC 
SDL doesn't support simultaneous blending and colorkey operations.  Typically what people do is turn off alpha blending or set the alpha channel to 0 for pixels that match the colorkey in their source art.

Let me know if you need help with either of these, or if you have a reason why you need both operations simultaneously.
Comment 2 Sam Lantinga 2013-08-05 02:45:43 UTC 
hello Sam,

thanks for the answer but a precision ! I dont know if I am clear.

I am talking about alpha per surface, not the Alpha channel.

Alpha + Colorkey does work correctly when using 16 bits per pixel : 
- colorkey colors are fully transparent.
- surface other colors are transparent (more or less, depending the alpha global value).

but this doesn't work when changing to 32 bits !