[gs-bugs] [Bug 691599] huge performance difference between jpeg and bit device for xl-raster-file

bugzilla-daemon at ghostscript.com bugzilla-daemon at ghostscript.com
Thu Sep 9 17:58:33 UTC 2010


Henry Stiles <henry.stiles at artifex.com> changed:

           What    |Removed                     |Added
                 CC|                            |michael.vrhel at artifex.com

--- Comment #1 from Henry Stiles <henry.stiles at artifex.com> 2010-09-09 17:58:25 UTC ---
Right because the ghostscript graphics library caches patterns fully rendered
(halftoned) so peculiar effects can occur when the pattern and halftone
interact.  The solution to this was to paint the pattern with width of least
common multiple of the halfone width and pattern width see pxink.c for details,
this can result in a significantly larger patterns and slower processing times.
 If you use the contone code path pxink.c:289 such that the "full width" equals
the "repeat width" the performance should be fine. 

The theoretical concerns are real, it is easy to imagine how the halftone
screen would be applied incorrectly when tiling an already halftoned pattern,
but actual practical problems seem to be rare.  PCL XL FTS 3.0 T421 panel 9 is
one of the few good examples I've found.  Also, I am not sure why we haven't
seen this problem in postscript or pdf which, as far as I know, neither
increase pattern size to avoid this problem.  All leading to the suggestion we
could disable the replicating code and document the rare problems that do occur

I've copied in Michael Vrhel our color expert, he may have some thoughts.

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