support colormap for raster layers on mapserver

[pvgenuchten]

colormaps for rasters is currently not implemented for mapfiles. would be nice to add it. the challenge is that a single rule generates multiple classes, the code seems to only able to handle a single class per rule.

bridge-style/bridgestyle/mapserver/fromgeostyler.py

Line 48 in c07754d

clazz = processRule(rule)

not sure how to improve that, suggestion for implementation of the rastersymbolizer

def _rasterSymbolizer(sl):
    style=[]

    if "colorMap" in sl:
        colMap = sl["colorMap"]
        prvQuantity = "0"
        for entry in colMap["colorMapEntries"]:
            stClass = {
                "NAME": entry["label"],
                "COLOR": entry["color"],
                "EXPRESSION": "([PIXEL]> {0} AND [PIXEL]<= {1})".format(prvQuantity, entry["quantity"]),
                "opacity": entry["opacity"],
            }
            prvQuantity = entry["quantity"]
            style.append(stClass)
    return style