[cairo] nearest neighborhood or bilinear interpolation

Bill Spitzak spitzak at d2.com
Mon Oct 30 12:14:37 PST 2006

Carlos Eduardo Rodrigues Diógenes wrote:

> Just to kill your curiosity I'm the co-maintainer of gnome-mag and I
> trying to discover if cairo can help us in the magnification process,
> since cairo supports lot's of back-ends, including Xrender and OpenGL,
> and is very easy to change from one to another, so an initial scale can
> be done in hardware and more intensive smoothing algorithms can be
> applied in software, this way when the user is scrolling the mouse
> around the desktop the magnifier screen get's updated quickly and only
> when the user stop to move the mouse ore intensive algorithms will be
> applied.

You are right, that is a 4th reason people request impulse filtering. So 
the reasons are:

1. Emulate the output of some other software.

2. Make a zoom produce "square pixels" rather than "blurry".

3. Make a non-integer translation round to the nearest integer.

4. Make it run faster.

I think in all these cases except #1 what is being requested is not 
exactly impulse filtering but a specific side effect of it.

I do think magnifier programs are very interested in making #2 work.

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