[poppler] Implement Type 4, 5, 6, 7 shadings using cairo mesh gradients

[Carlos Garcia Campos]

Excerpts from Thomas Freitag's message of mar ene 25 09:27:24 +0100 2011:
> Am 25.01.2011 09:15, schrieb Carlos Garcia Campos:
> > Excerpts from Albert Astals Cid's message of lun ene 24 19:53:50 +0100 2011:
> >> A Dilluns, 24 de gener de 2011, Thomas Freitag va escriure:
> >>> Am 24.01.2011 14:17, schrieb Carlos Garcia Campos:
> >>>> Cairo 1.11.2 has a new mesh pattern that can be used to implement 6/7
> >>>> type gradients. Adrian has an updated poppler branch that implements
> >>>> mesh gradients in cairo backend:
> >>>>
> >>>> http://cgit.freedesktop.org/~ajohnson/poppler/log/?h=mesh
> >>>>
> >>>> I've tried it and it works great, it fixes bugs #28836 and #32791 (and
> >>>> maybe others). I haven't pushed the patch yet becuase it contains
> >>>> minimal changes in Gfx.cc. If nobody objects I'll push it to master
> >>>> branch only.
> >>> I had a quick look at what Adrian has done in Gfc.cc, and think, that is
> >>> a little bit misusing of out->gouraudTriangleShadedFill( state, shading)
> >>> and out->patchMeshShadedFill( state, shading):
> >>>
> >>> When these functions returns gTrue, this indicates that all work has
> >>> already be done in the output device. How Adrian implements it is very
> >>> special to Cairo. But it is quite ease to change it:
> >>> Just move the lines
> >> Agreed with Thomas.
> > contentIsHidden() is private to Gfx, and all other patterns do the
> > clip and fill in Gfx
> Yeah, unfortunately contentIsHidden is private to Gfx, so probably there 
> should be a return if contentIsHidden() before calling the shading 
> routines in the output devices.

I'm not sure it's correct, the spec says:

When a piece of optional content in a PDF file is determined that it
shall be hidden, the following occurs:
 - The content shall not be drawn.
 - Graphics state operations, such as setting the colour,
   transformation matrix, and clipping, shall still be applied.

I think that's why we check whether content is hidden right before
filling. 

> But You're not true, that clip and fill 
> is done in Gfx, this is special to cairo which is the only device that 
> supports useFillColorStop() and can therefore use the clip and fill from 
> Gfx. At least in SplashOutputDev the done work (implemented by Christian 
> Feuersänger) in gouraudTriangleShadedFill would be overwritten and 
> probably causes wrong results.
> 
> Thomas
> >> Albert
> >>
> >>
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> >> poppler at lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/poppler
-- 
Carlos Garcia Campos
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x523E6462
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