I have a RGB image in QGIS that is the product of some raster analysis (e.g. QGIS's relief operation, results from sound/traffic models) to which I want to add a legend. I'd like to denote several RGB combinations with a individual labels. How should I go about it? I can't find a way to add legends to multiband color images in QGIS.
Ultimately I want to publish the image as a WMS service through GeoServer. Defining a legend on the server (through SLD?) is therefore also an option.