Bug 689309

Summary:	Problem with transparency reading PDF file
Product:	Ghostscript	Reporter:	Marcos H. Woehrmann <marcos.woehrmann>
Component:	PDF Interpreter	Assignee:	Timothy Osborn <tim.osborn>
Status:	NOTIFIED DUPLICATE
Severity:	normal	CC:	alex
Priority:	P1
Version:	master
Hardware:	PC
OS:	Linux
Customer:	1110	Word Size:	---
Attachments:	trans.pdf screenshot.png transillus.pdf

Description Marcos H. Woehrmann 2007-06-29 05:53:26 UTC

The customer reports and I've verified that the attached PDF file is not read
correctly with Ghostscript.  The customer reported this using 8.54, but 8.57 and
head (r8085) produce the same results.

The command line I used for testing:

  bin/gs -sDEVICE=ppmraw -sOutputFile=test.ppm ./trans.pdf

I've attached a screenshot comparing Acrobat 1.5 output to Ghostscript.

Comment 1 Marcos H. Woehrmann 2007-06-29 05:57:56 UTC

Created attachment 3088 [details]
trans.pdf

Comment 2 Marcos H. Woehrmann 2007-06-29 05:58:13 UTC

Created attachment 3089 [details]
screenshot.png

Comment 3 Ray Johnston 2007-06-29 08:46:05 UTC

Note that with a later rev than 8.57 (rev 8075) I see:

Error: /rangecheck in --.discardtransparencygroup--

Comment 4 Marcos H. Woehrmann 2007-06-29 10:27:13 UTC

Interestingly I do not see the rangecheck message:

% ~/artifex/ghostscript/trunk/gs/bin/gs -sOutputFile=test.ppm -sDEVICE=ppmraw trans.pdf
GPL Ghostscript SVN PRE-RELEASE 8.60 (2007-05-12)
Copyright (C) 2007 Artifex Software, Inc.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Processing pages 1 through 1.
Page 1
>>showpage, press <return> to continue<<

GS>quit
%

Comment 5 Timothy Osborn 2007-06-29 10:35:21 UTC

My results are as shown in screenshot.png. That is, job completes, but gs
produces bad output.

Comment 6 Timothy Osborn 2007-06-29 12:34:02 UTC

Created attachment 3100 [details]
transillus.pdf

Comment 7 Timothy Osborn 2007-06-29 12:44:50 UTC

It appears this is not a color compositing problem so much as a problem in the
PDF interpreter. When I take the original PDF (trans.pdf) and open it in
Illustrator CS2, make a single minor change to the PDF (move a cliprect a few
pixels) and save the PDF as a new PDF, this new PDF renders properly. Please see
the attachment transillus.pdf, which is the PDF that renders correctly. This
indicates that gs can handle the tranparecy operations, but something about the
structure of the original PDF is not being dealt with correctly. It it were
truly a compositing problem, the structural change in transillus.pdf would not
circumvent that problem.

Comment 8 Henry Stiles 2007-07-10 15:45:13 UTC

Tim, we request a better analysis here, we really can't conclude much from
comment #7.

Comment 9 Timothy Osborn 2007-07-11 08:45:33 UTC

There is a problem with the PDF interpretation when graphic states contain a
softmask dictionary. What happens is the softmask is never composited as it
never becomes part of a transparency group. Since compositing only takes place
when a group is "popped", the interpreter needs to recognize transparency groups
that are part of a graphics state. Currently the PDF interpreter only recognizes
groups that are part of a form group or imagemasks.

The reason transillus.pdf works correctly is that the file was restructured by
Illustrator in such as way that the SMask become part of a form group.

This is a duplicate of bug #688601

*** This bug has been marked as a duplicate of 688601 ***

Comment 10 Marcos H. Woehrmann 2011-09-18 21:47:04 UTC

Changing customer bugs that have been resolved more than a year ago to closed.