Fix (imagemask) : An optimization for imagemask with a shading color.

DETAILS :

This is a partial performance fix for 09-47L.PS .
It fixes the biggest performance flaw,
but a further optimization is still wanted.

The patch converts the image into a clipping path and then
renders entire shading at once through the clipping path.
The old code rendered entire shading color many times for
each rectangle of the mask.

1. The clip list accumulator device is made publicly accessible.

2. Provided a garbager descriptor for clip list accumulator device structure.

3. When an imagemask needs to render with a shading color,
gs_image_begin_typed replaces the target device with
the clip list accumulator device.

4. To provide a correct work of (3),
inserted a hook into gx_dc_pattern2_fill_rectangle,
which forwards the operation back to the device method.
It is done because normally that function calls
copy_mono with imagemak. Instead that, we need to accumulate
rectangles for the clipping path.

5. Introduced a new signal pattern_manage__is_cpath_accum,
which is used to detect the clip path accumulator device
under a forwarding device. Such case happens in (4)
when it renders a cached character with a shading color.

6. gs_image_cleanup performs the main work for rendering
the shading color through the clipping path.
Note that we need to pass the device color to it,
therefore it gets a new gs_state argument.
(Well, one may think that it can be passed
in a new field of gs_image_enum.
Actually that's not safe because an erroneus Postscript program
can change the current graphic state and
release the old one. After that the pointer
will point to the released structure and
cause a heap inconsistency).

EXPECTED DIFFERENCES :

None.

git-svn-id: http://svn.ghostscript.com/ghostscript/trunk@7120 a1074d23-0009-0410-80fe-cf8c14f379e6

0 files changed, 0 insertions, 0 deletions