[cairo] Projective transforms

Maarten Bosmans mkbosmans at gmail.com
Wed Aug 11 13:16:28 PDT 2010

2010/8/11 Benjamin Otte <otte at redhat.com>:
> On Wed, 2010-08-11 at 09:47 +0200, Maarten Bosmans wrote:
>> Does this mean that projective transformations are possible in Cairo?
>> What would be required to use it?
> It means projective transforms are possible in Pixman. Using them in
> Cairo has been a desire for a while, but no one has yet attempted to
> implement it.

I could not find the implementation pixman. The file pixman-matrix.c
only deals with 3x3 matrices used for affine transformations. Am I
missing something?

The SVG 1.1 spec only defines affine transformations. A proposed
extension to include projective transformations is a working draft:
That page nicely lays out the use of homogeneous coordinates in 2D and
3D and how the conversion works. It could be used as a guide for
implementing in pixman and of course also for the cairo svg surface.

If the general outline of implementing such a thing in cairo (and
pixman?) becomes clear, I can certainly try to whip up some patches.
My main motivation would be to enable the rendering of animated text
in a projective plain, like the classic Star Wars prologue.


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