[Poppler-bugs] [Bug 10942] spurious horizontal stripes in color gradients

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=10942





--- Comment #18 from Adrian Johnson <ajohnson at redneon.com>  2009-06-03 14:32:39 PST ---
(In reply to comment #16)
> (In reply to comment #15)
> > Created an attachment (id=26402)
 --> (http://bugs.freedesktop.org/attachment.cgi?id=26402) [details] [details]
> > Implement axialShadedFill() in cairo backend using cairo linear gradient
> > patterns
> > 
> >  poppler/CairoOutputDev.cc |  297 +++++++++++++++++++++++++++++++++++++++++++++ 
> >  poppler/CairoOutputDev.h  |    6 +                                             
> >  2 files changed, 303 insertions(+), 0 deletions(-)
> > 
> > This patch implements linear gradients in cairo backend. I'm not a cairo guru
> > so I'm not sure it's completely right, it fixes the problem with the first
> > attachment. 
> > 
> 
> The use of cairo looks fine. Would it be better to avoid duplicating the
> bisection code from Gfx and instead add a new axial shading OutputDev function
> that provides the coordinates of each stop?
> 

On closer inspection the use of cairo is less than ideal. It would be better to
use the actual stops in the shading in the case of linear interpolation (Type 2
Exponential functions with N=1) and fallback to bisection for other cases. This
would allow cairo to do the linear interpolation where possible.


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