Bug 702074

Summary: visible seams between adjoining shapes due to anti-aliased blending
Product: MuPDF Reporter: Krzysztof Kowalczyk <kkowalczyk>
Component: mupdfAssignee: MuPDF bugs <mupdf-bugs>
Status: UNCONFIRMED ---    
Severity: normal    
Priority: P4    
Version: master   
Hardware: PC   
OS: Windows 10   
Customer: Word Size: ---
Attachments: Repro file

Description Krzysztof Kowalczyk 2020-02-01 01:48:55 UTC 
Created attachment 18827 [details]
Repro file

Reported in https://github.com/sumatrapdfreader/sumatrapdf/issues/913

The blue gradient at the top (behind LANL) is more "bandy" than rendered by e.g. Chrome (i.e. Foxit).
Comment 1 Krzysztof Kowalczyk 2020-02-01 02:02:05 UTC 
Another file that likely has the same root cause is in https://github.com/sumatrapdfreader/sumatrapdf/issues/912
Comment 2 Tor Andersson 2025-10-15 09:19:02 UTC 
The white stripes are caused by anti-aliased rendering drawing multiple thin rectangular paths. Each rectangle has semi-transparent edges that let the white background show through due to anti-aliasing; and when these are drawn in sequence these white "gaps" appear.

If you render without anti-aliasing the gradient is rendered fully solid.

This is an unfortunate side-effect of implementing anti-aliasing using coverage-based opacity instead of using multi-sampling (rendering at a higher resolution and down-sampling the final result).

The only "solutions" to this problem is disabling anti-aliasing either locally (by grid-fitting rectangle fills so they land perfectly on the pixel grid) or globally.
Comment 3 Tor Andersson 2025-11-03 12:32:02 UTC 
*** Bug 702083 has been marked as a duplicate of this bug. ***