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

[Thomas Freitag]

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

+ double xMin, yMin, xMax, yMax;
+
+ // get the clip region bbox
+ state->getUserClipBBox(&xMin, &yMin, &xMax, &yMax);
+ state->moveTo(xMin, yMin);
+ state->lineTo(xMin, yMax);
+ state->lineTo(xMax, yMax);
+ state->lineTo(xMax, yMin);
+ state->closePath();
+ if (!contentIsHidden())
+ out->fill(state);
+ state->clearPath();

to CairoOutputDev::gouraudTriangleShadedFill respectively to 
CairoOutputDev::patchMeshShadedFill, i.e. if the actual implementation 
of gouraudTriangleShadedFill in CairoUtputDev would be renamed to 
formerGouraudTriangleShadedFill then do it like

GBool CairoOutputDev::gouraudTriangleShadedFill(GfxState *state, 
GfxGouraudTriangleShading *shading) {
         if (formerGouraudTriangleShadedFill(state, shading)) {
             double xMin, yMin, xMax, yMax;

              // get the clip region bbox
              state->getUserClipBBox(&xMin, &yMin, &xMax, &yMax);
              state->moveTo(xMin, yMin);
              state->lineTo(xMin, yMax);
              state->lineTo(xMax, yMax);
              state->lineTo(xMax, yMin);
              state->closePath();
              fill(state);
              state->clearPath();
              return gTrue;
         } else
             return gFalse;
}

patchMeshShadedFill simular. Then You don't need to change Gfx, and it 
fits to the other shading routines.


Thomas


> Regards,
>
>
>
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