[OLPC-Games] [sugar] Cairo tile engine, and accessing 565 buffers from cairo and C

Kent Quirk kent_quirk at cognitoy.com
Tue Apr 17 21:04:27 EDT 2007

Bert Freudenberg wrote:
> On Apr 17, 2007, at 15:53 , Dan Williams wrote:
>> Correct; about the only thing you can do here is use create_similar 
>> () on
>> the xlib _window_ surface, draw your 24bpp image surface to that, and
>> cache the 565 xlib surface for all further drawing.  Note that you  
>> will
>> _not_ get alpha because the surface is 565.
> Supposed we switched to 1555 as suggested by some, we would have one  
> bit of alpha, which would be very useful for sprites in games. Given  
> the small pixel size this should also look pretty satisfactory even  
> though there is only 1 bit of alpha and no real blending.
> So is this still planned or are you going to switch to 24 bits once  
> the LX arrives?
I don't know what the plans are, but just to throw in my two cents:

I've been working on a commercial project that is using 1555, and I've 
also used 565. One-bit alpha is...better than none at all, and better 
than a transparent color in a palette, but significantly inferior to 
8-bit alpha.

565 plays havoc with grayscales and gradients -- you can't get them smooth.

So if it's gonna be 16-bit and there's a choice, I strongly vote for 1555.


Kent Quirk           I'm making a game about global warming.
Game Architect                        Track the progress at:
CogniToy                http://www.cognitoy.com/meltingpoint

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