[cairo] PDF Blend modes

Carlos Garcia Campos carlosgc at gnome.org
Wed Jun 17 03:50:08 PDT 2009

Hi all, 

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]. I've also
changed composite-test adding more operators[3]. 

Cairo merge was much easier, just a couple of simple conflicts, so this
time I could rebase blend-mode branch from master. Tests for blend-modes
are currently broken, though. A git public repository is also available
at [4]. 

And I finally wrote the code needed in poppler [5]. I've used a test
file[6] to compare the output of poppler[7], xpdf[8] and acroread[9].
Although the poppler output doesn't look right, I think the compositing
is correct in most of the cases, but for some reason (probably another
bug in poppler) it's applied on the whole image instead of just the part
with blue background. 

So, what's still left to do in cairo/pixman? is there anything else I
can do to help?

[1] http://lists.cairographics.org/archives/cairo/2008-October/015339.html
[2] git://people.freedesktop.org/~carlosgc/pixman (blend-mode branch)
[3] http://people.freedesktop.org/~carlosgc/composite-test.png
[4] git://people.freedesktop.org/~carlosgc/cairo (blend-mode branch)
[5] git://people.freedesktop.org/~carlosgc/poppler (blend-mode branch)
[6] http://acroeng.adobe.com/Test_Files/images/transparency/rgbrasterobjecttypes_109.pdf
[7] http://people.freedesktop.org/~carlosgc/poppler-blend-mode.png
[8] http://people.freedesktop.org/~carlosgc/xpdf-blend-mode.png
[9] http://people.freedesktop.org/~carlosgc/acroread-blend-mode.png

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