[Pixman] On sampling (Re: Add a new benchmarker targeting affine operations)

[Pekka Paalanen]

On Fri, 24 Apr 2015 13:00:19 -0700
Bill Spitzak <spitzak at gmail.com> wrote:

> On 04/24/2015 07:31 AM, Pekka Paalanen wrote:
> 
> > Would it be good to set a rule of thumb, that when you are scaling
> > images, first compute the final size, and then compute the
> > transformation paramaters for Pixman, regardless from which one you
> > start with?
> 
> If I understand what you are asking for, the answer is no.
> 
> When scaling images do not be confused by the pixel size or pixel 
> centers. The correct transform is the one that places the outer corners 
> of the source image (ie integers 0,0 and w,h for the entire contents of 
> a w,h sized image) at the outer corners of the desired destination 
> quadrilateral.

That is exactly what I meant.


Thanks,
pq