[poppler] Implemented Type 4/5 shading for Splash Device

[Albert Astals Cid]

A Dilluns, 14 de juny de 2010, Christian Feuersaenger va escriure:
> Dear Poppler Developers,

Hi Chrisitian

> 
> I found that the actual implementation of Type 4 or Type 5 interpoalted
> shadings in xpdf/libpoppler are extremely slow and do not display all
> shadings correctly (parameterized patches with large triangles are often
> wrong).
> 
> I have written a stable patch for both issues: it is now about 5 times
> faster and displays parameterized patches correctly. It is a small
> bugfix combined with a tweaked the triangle refinement.
> 
> Furthermore, I have a prototype which implements *real* linear
> interpolation for these shadings. It is very fast and looks considerably
> better than the piecewise constant approximation introduced by triangle
> refinements. It works pretty well up to now. I implemented low level
> support for these shadings and specialized the SplashOutputDev for
> rendering triangle interpolations, i.e. it works for screen display and
> for bitmap output. Quality and display speed match the one of acrobat
> reader.
> 
> I am sure my additions are valueable and propose them for usage in
> libpoppler: the bugfix/speed improvement is directly usable and stable
> and the lowlevel shader will need some more time. I could also use some
> advice to get the integration with transparency, blending and whatever
> correctly. I started with the xpdf sources, so I would also appreciate
> any hints how you communicate changes between xpdf and libpoppler if you
> are interested in my proposal.

Yes, we are interested in your patches, basically what we would need you is to 
provide a patch over poppler sources, you can choose wheter you want to make 
it against git master branch, git poppler-0.14 branch or the released 0.14.0 
tarball.

Also it would be interesting to have the PDF you have used for testing.

Thanks,
  Albert

> 
> Best regards
> 
> Christian
> 
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