Symbology of non-RGB rasters

[jmacura]

Raster file with single-band and arbitrary floating point values cannot be uploaded to Layman. Such files are common in data processing, e.g. as DEM files.

One such file is the following: https://hub4everybody.com/client/rest/workspaces/macurajan/layers/cz_by_raster
publication status is "incomplete", hence the WMS service returns error when map is requested:

<?xml version="1.0" encoding="UTF-8"?><ServiceExceptionReport version="1.3.0" xmlns="http://www.opengis.net/ogc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/ogc https://hub4everybody.com/layman-proxy/geoserver/schemas/wms/1.3.0/exceptions_1_3_0.xsd">   <ServiceException>
      java.lang.NullPointerException
</ServiceException></ServiceExceptionReport>

Testing data attached here (TIF + SLD).
non-rgb-rasters_TIF+SLD.zip

Expected behaviour:

1. do not fail publication
2. serve WMS ...

• as symbolised by SLD or QML file if provided or
• in a grayscale by mapping input raster values to standard 0-1 (0-255) range.

[index-git]

Publishing this layer fails as GeoServer fails to render WMS GetMap for thumbnail. We found out, that when <sld:Opacity>0.8</sld:Opacity> line is removed from style file, thumbnail is generated and layer published successfully. Workaround is to move opacity to each ColorMapEntry item, which also works ok.