Bug 691372 - pngalpha output background is not transparent when resolution is above a certain value
Summary: pngalpha output background is not transparent when resolution is above a cert...
Status: RESOLVED DUPLICATE of bug 692224
Alias: None
Product: Ghostscript
Classification: Unclassified
Component: General (show other bugs)
Version: 8.71
Hardware: PC Linux
: P4 major
Assignee: Michael Vrhel
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2010-06-08 10:31 UTC by Michael Witrant
Modified: 2011-10-05 07:19 UTC (History)
2 users (show)

See Also:
Customer:
Word Size: ---


Attachments
Sample A4 PDF (891 bytes, application/binary)
2010-06-08 10:31 UTC, Michael Witrant
Details

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Description Michael Witrant 2010-06-08 10:31:08 UTC
Created attachment 6357 [details]
Sample A4 PDF

When converting a PDF to PNG using the pngalpha device, the background is transparent when the resolution is below a certain value, and white when it's above. The value depends on the page size of the PDF.

For example with the test_A4.pdf attached (A4 page size), this command will output the expected transparent background :
 gs -q -sDEVICE=pngalpha -dBATCH -dNOPAUSE -r160 -sOutputFile=test_A4_160.png test_A4.pdf
But this command will output a white background :
 gs -q -sDEVICE=pngalpha -dBATCH -dNOPAUSE -r161 -sOutputFile=test_A4_161.png test_A4.pdf

Any resolution below 160 will produce a transparent background, and any resolution above 161 will produce a white background.

When converting an A5 PDF, the background is transparent only for resolutions 227 and lower.
Comment 1 Michael Witrant 2010-06-09 23:30:28 UTC
It looks like the transparent background doesn't work when banding is used. Setting a big value to MaxBitmap is a workaround.
Comment 2 Ray Johnston 2010-09-27 00:53:10 UTC
I think with recent work on PDF transparency + tags support for both the page
and clist (banding) mode, that Michael may have already fixed this, or if not,
it will be in areas he has recently considered.
Comment 3 Daniel Wehrle 2011-01-13 11:57:47 UTC
I have still the problems in 9.00 on win.
Comment 4 Erik Johnson 2011-10-05 06:46:00 UTC
Still occurs in 9.04 (built from source on Mac OS X). It's not specific to PDF, occurs for postscript also.
Comment 5 Michael Vrhel 2011-10-05 07:19:08 UTC
This is a duplicate of Bug 692224

*** This bug has been marked as a duplicate of bug 692224 ***