Weird styling for png8 and antialias:none

Description

This bug occurs for WMS request if the format of image is png8 and format_options is set to antialias:none.
The styling of features on the map and background color is changing a kind of randomly. It depends only on the "BBOX" parameter.
Reproduction is easy: set the output format: openlayers, change image format to png8 and antialiasing to Disabled (antialias:none). See the animated gif:

Reconstruction 2:

Request 1:

http://localhost:8080/geoserver217/topp/wms?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng8&TRANSPARENT=true&LAYERS=topp%3Astates&exceptions=application%2Fvnd.ogc.se_inimage&FORMAT_OPTIONS=antialias%3Anone&CRS=EPSG%3A4326&STYLES=&WIDTH=768&HEIGHT=330&BBOX=29.2236328125%2C-110.23681640625%2C32.84912109375%2C-101.79931640625

 

Request 2:

http://localhost:8080/geoserver217/topp/wms?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng8&TRANSPARENT=true&LAYERS=topp%3Astates&exceptions=application%2Fvnd.ogc.se_inimage&FORMAT_OPTIONS=antialias%3Anone&CRS=EPSG%3A4326&STYLES=&WIDTH=768&HEIGHT=330&BBOX=27.333984375%2C-113.62060546875%2C34.5849609375%2C-96.74560546875

 

Both requests differ in BBOX parameter only. The colors of features on the map and background color depend on the BBOX parameter only.

Additionally please adjust vendor parameter values from antialias(ing):off to antialias:none. It is incorrectly documented: https://docs.geoserver.org/latest/en/user/services/wms/vendor.html
Regards

Bartek

Environment

geoserver version 2.17.0, tomacat9, Win Server 2019 64bit, openjdk version "1.8.0_252"

Assignee

Unassigned

Reporter

Bartek Burkot

Triage

Fix versions

None

Affects versions

Components

Priority

Medium
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