Bug 691925 - Additional differences in dithered output with ps2write
Summary: Additional differences in dithered output with ps2write
Status: CONFIRMED
Alias: None
Product: Ghostscript
Classification: Unclassified
Component: PS Writer (show other bugs)
Version: master
Hardware: PC Linux
: P4 enhancement
Assignee: Ken Sharp
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2011-02-02 03:32 UTC by Marcos H. Woehrmann
Modified: 2011-02-07 15:46 UTC (History)
0 users

See Also:
Customer:
Word Size: ---


Attachments
screenshot.png (53.93 KB, image/png)
2011-02-02 03:32 UTC, Marcos H. Woehrmann
Details

Note You need to log in before you can comment on or make changes to this bug.
Description Marcos H. Woehrmann 2011-02-02 03:32:24 UTC
Created attachment 7186 [details]
screenshot.png

Pages 5, 6, and 7 of the ps3cet file 09-40.PS look very different when converted to pkmraw directly and via ps2write (see attached screenshot.png, the direct image is on the left, via ps2write is on the right).

Command lines:

  ./bin/gs -o test.ps  -sDEVICE=ps2write -r300 ./ps3cet/09-40.PS
  ./bin/gs -o test.pkm -sDEVICE=pkmraw   -r300 ./test.ps

  ./bin/gs -o test2.pkm -sDEVICE=pkmraw  -r300 ./ps3cet/09-40.PS
Comment 1 Ken Sharp 2011-02-07 15:46:46 UTC
It looks like these pages are using type 10 halftones. These were introduced in 2015, so the ps2write code assumes that they can't be used (not baseline level2).

It seems that this causes a fallback to an image, which uses the current default halftone to render instead of the custom type 10 halftone. This results in the difference in output.

I think it would be useful to preserve type 10 halftones, but this is an enhancement, not a bug, really.