[Poppler-bugs] [Bug 13487] Slow rendering of file with lot of group objects

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=13487

--- Comment #4 from thomasf <Thomas.Freitag at alfa.de> 2012-04-16 02:57:53 PDT ---
I had a look into that sample: It seems, as if cairo produced a lot a
transparency group entries in the PDF, which slows down rendering in splash.
According to a the PDF spec (11.4.4 Group Compositing Computations, page 337,
note 5):

As a result of these corrections, the effect of compositing objects as a group
is the same as that of compositing them separately (without grouping) if the
following conditions hold:
1. The group is non-isolated and has the same knockout attribute as its parent
group (see 11.4.5, "Isolated Groups," and “Knockout Groups”).
2. When compositing the group’s results with the group backdrop, the Normal
blend mode is used, and the shape and opacity inputs are always 1.0.

it should be quite easy to recognize this in the splash transparency group
functions and "remove" this behaviour in splash. I already tested it, hard
coding transpGroup to gFalse in Gfx: rendering time less than one second,
result seems to be the same.

I'll try to implement it for 0.22.0

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