Bug 698672 - Odd rendering with new scan converter and GraphicsAlphaBits
Summary: Odd rendering with new scan converter and GraphicsAlphaBits
Status: NOTIFIED FIXED
Alias: None
Product: Ghostscript
Classification: Unclassified
Component: Graphics Library (show other bugs)
Version: master
Hardware: PC Windows 7
: P1 normal
Assignee: Robin Watts
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-10-18 06:51 UTC by Ken Sharp
Modified: 2017-10-31 12:33 UTC (History)
1 user (show)

See Also:
Customer: 531
Word Size: ---

Attachments
much reduced sampl efile (207.37 KB, application/pdf)
2017-10-18 06:51 UTC, Ken Sharp 		Details
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Description Ken Sharp 2017-10-18 06:51:46 UTC 
Created attachment 14397 [details]
much reduced sampl efile

The customer reports that the file when rendered with:

gswin32c.exe -q -dNOPAUSE -sDEVICE=tiff24nc -r600x600 -dGraphicsAlphaBits=4 -sOutputFile=5.tif GraphicsAlpha.pdf

produces odd gray sections in the body of the black line. This is visible throughout the line section though the customer bitmap focuses on teh 'U' shaped section near the centre of the line.

Using the old scan covnerter (-dSCANCONVERTERTYPE=0) ro not using GraphicsAlphaBits renders a solid line.
Comment 1 Ray Johnston 2017-10-18 12:22:34 UTC 
Correct the customer number and priority
Comment 2 Robin Watts 2017-10-19 07:57:01 UTC 
Fixed in commit:

commit 684f73e8deefacb2aa5d2277f3154b68809b2ab7 (HEAD -> master, golden/master)Author: Robin Watts <robin.watts@artifex.com>
Date:   Thu Oct 19 13:01:46 2017 +0100

    Bug 698672: Fix new scanconverter/alphabits interaction.

    The alphabits mechanism relies on the scan converter not
    writing trapezoids so tall as to cause its line buffers
    to flush too early.

    This is achieved by honoring the max_band_height field in
    the device header. Previously the new scan converter was
    ignoring this. Here we alter the code to pay attention to
    it.
Comment 3 Chris Liddell (chrisl) 2017-10-31 12:33:49 UTC 
*** Bug 698713 has been marked as a duplicate of this bug. ***