GeoServer Integration: rendering transformations - GeoServer Training
Geometry transformations have been added almost one year ago to GeoTools to allow the application of a filter function to the geometry before rendering it. This allows for quite a bit of flexibility, yet still fails to address some needs: transformations that do need to take into account more than one feature at a time transformations that perform raster to vector transformations, like contouring.
https://docs.geoserver.geo-solutions.it/edu/en/wps/rendering_tx.html
