[Poppler-bugs] [Bug 47706] Exporting pdf from LibreOffice with smooth gradient displays striped in Evince, shows correctly in Adobe Reader

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=47706

--- Comment #8 from Adrian Johnson <ajohnson at redneon.com> 2012-03-23 21:44:57 PDT ---
Getting back on topic...

The problem of seams between adjacent fills is a well known limitation of
cairo. There has been plenty written about it on the cairo list [1][2]. It is
caused by the incremental antialiasing used by cairo. There is no simple fix.
It is inherent in the design [3]. There have been various work arounds
suggested (eg full scene antialiasing) but they are all slow and resource
intensive.

I don't know how acroread makes it work. It might be something to do with
keeping shape and opacity separate [4].

There is an experimental patch in bug 19760 where I tried fixing the problem by
aligning fills to device pixels but in some cases this made the problem worse.

The best (and quicker) solution would be for LibreOffice to make use of native
PDF gradients to draw gradients. There have been other reports of OpenOffice's
faux gradients causing problems when printing [5] or with other viewers
including acroread [6].

[1] http://lists.cairographics.org/archives/cairo/2005-November/005726.html
[2] http://lists.cairographics.org/archives/cairo/2006-March/006558.html
[3] http://lists.cairographics.org/archives/cairo/2008-January/012694.html
[4] http://lists.cairographics.org/archives/cairo/2006-April/006615.html
[5] http://www.oooforum.org/forum/viewtopic.phtml?t=60690
[6] https://issues.apache.org/ooo/show_bug.cgi?id=65970

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