Bug 691745 - White line in image
Summary: White line in image
Status: NOTIFIED INVALID
Alias: None
Product: Ghostscript
Classification: Unclassified
Component: Images (show other bugs)
Version: master
Hardware: All All
: P1 normal
Assignee: Robin Watts
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2010-11-03 16:39 UTC by Ray Johnston
Modified: 2011-10-02 02:34 UTC (History)
0 users

See Also:
Customer: 532
Word Size: ---


Attachments
Wline_BB.pdf (152.12 KB, application/pdf)
2010-11-03 16:39 UTC, Ray Johnston
Details
cutdown.pdf (17.28 KB, application/pdf)
2010-11-03 18:13 UTC, Robin Watts
Details

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Description Ray Johnston 2010-11-03 16:39:20 UTC
Created attachment 6863 [details]
Wline_BB.pdf

The attached PDF file has a White line in the middle of the image when run
with:

   gs -r600 -sDEVICE=png16m -o wline.png Wline_BB.pdf
Comment 1 Robin Watts 2010-11-03 18:13:09 UTC
Created attachment 6864 [details]
cutdown.pdf

A more cutdown version of the file.
Comment 2 Robin Watts 2010-11-03 18:23:45 UTC
As might be expected from looking at the file, the image with the line in it is in fact 2 images that are supposed to be displayed abutting one another.

The top image starts at 4541.67 and goes upwards. The bottom image starts at 4118.67 and extends upwards for a height of 446. At first glance therefore the two images therefore overlap and there should be no white line.

In fact, the bottom image is masked. Both the image and its mask are 75 pixels high, and the top 5 pixels in the image are entirely masked out.

This means that 'painting' portion of that image will extend upwards by 446*70/75 pixels = 416.266667 pixels. Thus we expect the bottom image to cover from 4118.67 to 4534.93667.

This leaves a gap between 4534.93 and 4541.67, which is manifested in the rendering as a blank line.

I think gs is doing the right thing here...
Comment 3 Robin Watts 2010-11-03 18:34:47 UTC
Acrobat 9 Pro gives the same white line when exported to a TIFF at 600dpi. It gives *worse* white lines when rendered to the screen. So I don't think this bug is valid.