[SDL] CVS Update (alpha blending)

Sam Lantinga slouken at devolution.com
Sun Apr 2 17:21:09 PDT 2000


I happened to need alpha blending for Pirates Ho!

The latest CVS snapshot has 32-bit alpha channel blits nearly twice as fast
as they were before.  RLE accelerated blits are also a little bit faster.

http://www.devolution.com/~slouken/SDL/cvs.html

I tested the code by loading a PNG file created by GIMP with the SDL_image
library, and then blitting the resulting image to the screen.  I properly
saw the image being blended with the destination surface, according to the
alpha channel information stored in the PNG image.

I recommend that you keep images with alpha channel information as 32-bits,
and do not convert them to the display format.  If you convert an image,
you will lose the alpha channel information, and the alpha blits are optimized
for 32 bpp source images.

Enjoy!
	-Sam Lantinga, Lead Programmer, Loki Entertainment Software



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