[SDL] Blitting

[David Olofson]

On Wednesday 12 February 2003 19.25, David Olofson wrote:
[...]

Uhm, just in case you didn't notice:

> 	/* Calculate filter core */
> 	x -= 8;
> 	y -= 8;

This is a (-.5, -.5) pixel offset, to compensate for the fact that 
interpolation is done from a grid of infinitely small pixels, while 
output is to a grid of full size pixels. Without this, you'd get 
images shifted half a pixel to the left and half a pixel up. 
(Source/scaled pixels, that is.)


//David Olofson - Programmer, Composer, Open Source Advocate

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