Color Ramps
Mapserver has the ability to display raster data using color ramps which is useful for displaying Hillshades, Digital Elevation Models, and other quantitative data.
CLASS
EXPRESSION ([pixel] >= 1524 AND [pixel] < 1621)
STYLE
COLORRANGE 179 240 240 255 255 180 #color start RGB and end RGB
DATARANGE 1524 1621 #the data range is normally set to the class expression range
RANGEITEM "pixel" # pixel is the elevation value in a DEM
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1524 AND [pixel] < 1621)
STYLE
COLORRANGE 175 240 233 255 255 179
DATARANGE 1524 1621
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1621 AND [pixel] < 1670)
STYLE
COLORRANGE 255 255 190 0 128 70
DATARANGE 1621 1670
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1670 AND [pixel] < 1713)
STYLE
COLORRANGE 0 128 70 250 180 0
DATARANGE 1670 1713
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1713 AND [pixel] < 1753)
STYLE
COLORRANGE 250 180 0 130 0 0
DATARANGE 1713 1753
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1753 AND [pixel] < 1803)
STYLE
COLORRANGE 130 0 0 110 60 20
DATARANGE 1753 1803
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1803 AND [pixel] < 1870)
STYLE
COLORRANGE 110 60 20 180 180 180
DATARANGE 1803 1870
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
EXPRESSION ([pixel] >= 1870)
STYLE
COLORRANGE 180 180 180 255 255 252
DATARANGE 1870 1997
RANGEITEM "pixel"
END #STYLE
END #end class
CLASS
STYLE
COLORRANGE 0 0 0 252 252 252
DATARANGE 153 204 #note: the data range here does not have to be the same as the range in the source data.
RANGEITEM "pixel"
END #Style
END #Class
This information is provided from Even Rouault
An alternate way is to use the gdaldem utility from GDAL with the color-relief mode : http://www.gdal.org/gdaldem.html
As a bonus, you can avoid generating a full new raster, by outputing to a VRT file (an XML file) that will only contain the LUT to map the elevations to colors.
gdaldem color-relief n43.dt0 dem.pct n43_pct.vrt -of vrt
with dem.pct :
3500 white
2500 235:220:175
50% 190 185 135
700 240 250 150
0 50 180 50
nv 0 0 0 0
generates n43_pct.vrt :
<VRTDataset rasterXSize="121" rasterYSize="121">
<SRS>GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY["EPSG","4326"]]</SRS>
<GeoTransform> -80.00416666666666, 0.008333333333333333, 0,
44.00416666666666, 0, -0.008333333333333333</GeoTransform>
<VRTRasterBand dataType="Byte" band="1">
<ColorInterp>Red</ColorInterp>
<ComplexSource>
<SourceFilename relativeToVRT="1">n43.dt0</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize="121" RasterYSize="121" DataType="Int16"
BlockXSize="1" BlockYSize="121"/>
<SrcRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<DstRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<LUT>-32767:0,0:50,267.5:190,700:240,2500:235,3500:255</LUT>
</ComplexSource>
</VRTRasterBand>
<VRTRasterBand dataType="Byte" band="2">
<ColorInterp>Green</ColorInterp>
<ComplexSource>
<SourceFilename relativeToVRT="1">n43.dt0</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize="121" RasterYSize="121" DataType="Int16"
BlockXSize="1" BlockYSize="121"/>
<SrcRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<DstRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<LUT>-32767:0,0:180,267.5:185,700:250,2500:220,3500:255</LUT>
</ComplexSource>
</VRTRasterBand>
<VRTRasterBand dataType="Byte" band="3">
<ColorInterp>Blue</ColorInterp>
<ComplexSource>
<SourceFilename relativeToVRT="1">n43.dt0</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize="121" RasterYSize="121" DataType="Int16"
BlockXSize="1" BlockYSize="121"/>
<SrcRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<DstRect xOff="0" yOff="0" xSize="121" ySize="121"/>
<LUT>-32767:0,0:50,267.5:135,700:150,2500:175,3500:255</LUT>
</ComplexSource>
</VRTRasterBand>
</VRTDataset>
that you can use as a raster name in your mapfile.
