[cairo] PDF Blend modes

Carlos Garcia Campos carlosgc at gnome.org
Wed Jun 17 08:13:12 PDT 2009

El mié, 17-06-2009 a las 14:25 +0200, Soeren Sandmann escribió:
> Hi,
> > I'm trying to implement the missing features in poppler cairo backend
> > (specially those that are present in splash backend). When I asked ickle
> > about blend mode operators in cairo, he told me that Company had started
> > to implement it some time ago[1]. So, I have taken Company's repos in
> > order to update them and try to use the new cairo operators in poppler. 
> > 
> > First I tried to rebase blend-mode pixman branch from current master,
> > but it was quite painful, too many conflicts, so I finally merged it as
> > a single patch. I've set up a public repository for this [2].
> This looks great; thanks for doing this!
> I can definitely understand why you decided to merge it as one big
> patch, but I'd really like to see it broken down a bit if
> possible. Benjamin's tree had a lot of small commits; if we can
> preserve at least some of them, that would be nice.

I finally rebased your repo to current master, see the new repo here:


> > I've also changed composite-test adding more operators[3]. 
> Nice!
> > So, what's still left to do in cairo/pixman? is there anything else I
> > can do to help?
> See this mail:
>    http://lists.cairographics.org/archives/cairo/2008-December/015931.html
> I did some work on top of Benjamin's branch in the blendmode branch of
> this repo:
>         http://cgit.freedesktop.org/~sandmann/pixman/log/?h=blendmode
> The things that remain to be done starting from that:
> * Rebase to current master, preserving as much history as possible.


> * Review that what I did makes sense (both the code and the math in
>   the comment I added).
> * Use floating point in the HSL modes
>   Because I'm not sure that the overflow protection we have right now
>   is correct.
> * Getting rid of component alpha versions of HSL and
>   return_if_fail()ing if you to use them with a component alpha
>   mask. [1]
>   [1] They could be done in ways that would be mathematically
>   consistent with the other blend modes, but I don't know that it
>   would make any visual sense. I could be convinced otherwise, though.
> * There is an "#undef Set" which should be "#undef Sat"


> Thanks,
> Soren


Carlos Garcia Campos
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x523E6462
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