Re: [mapserver-users] WMS - Change color map of a DEM dynamically

Tue, 30 May 2017 17:15:06 -0700 

Here is a good explanation:

https://lists.osgeo.org/pipermail/gdal-dev/2014-May/039091.html

On 5/30/2017 8:09 PM, Stephen Woodbridge wrote:
I don't use QGIS so maybe someone else has some idea how to do what you want with that. I think I might try something along these lines:
Create a GDAL VRT file for each theme and add appropriate color tables for them. You might need to write a script to generate the color ramps as color table entries, but once you have them you should be good.
The VRT files can all reference the same DEM.tif file so you are only create VRT file for the color tables.
Then create appropriate layers in the mapfile each referencing one of the VRT files. Then the user can select the appropriate WMS layer from the mapfile dor the styling they want. 

-Steve W

On 5/30/2017 7:56 PM, Eduardo Kanegae wrote:

Hi,
I'm running MapServer 7.0.5 with GDAL 2.2.0 (CentOS x64) and have a 6Gb DEM tiff(float32) with overviews. Currently I set up a color ramp in QGIS based on values/colors of some GRASS color tables such as ETOPO2, SRTM and Terrain. Then in mapfile I used a color ramp (colorrange, datarange, rangeitem) coying colors and limit values from QGIS themes.
I'd like to let users to dynamically change the WMS raster output using QGIS. Then, it could avoid to duplicating LAYERS declarations such as "dem_srtmtheme", "dem_etopo2theme" and so on. 
Or this (such as SLD) will be possible only for 8bit rasters and vectors?

thanks in advance.

Here's the dump(gdalinfo) of my raster file:

Driver: GTiff/GeoTIFF
Files: /myfile.tif
        /myfile.tif.ovr
Size is 45369, 38050
Coordinate System is:
PROJCS["SIRGAS 2000 / UTM zone 23S",
     GEOGCS["SIRGAS 2000",
DATUM["Sistema_de_Referencia_Geocentrico_para_las_AmericaS_2000", 
             SPHEROID["GRS 1980",6378137,298.257222101,
                 AUTHORITY["EPSG","7019"]],
             TOWGS84[0,0,0,0,0,0,0],
             AUTHORITY["EPSG","6674"]],
         PRIMEM["Greenwich",0,
             AUTHORITY["EPSG","8901"]],
         UNIT["degree",0.0174532925199433,
             AUTHORITY["EPSG","9122"]],
         AUTHORITY["EPSG","4674"]],
     PROJECTION["Transverse_Mercator"],
     PARAMETER["latitude_of_origin",0],
     PARAMETER["central_meridian",-45],
     PARAMETER["scale_factor",0.9996],
     PARAMETER["false_easting",500000],
     PARAMETER["false_northing",10000000],
     UNIT["metre",1,
         AUTHORITY["EPSG","9001"]],
     AXIS["Easting",EAST],
     AXIS["Northing",NORTH],
     AUTHORITY["EPSG","31983"]]
Origin = (268724.500000000000000,7485552.500000000000000)
Pixel Size = (1.000000000000000,-1.000000000000000)
Metadata:
   AREA_OR_POINT=Area
Image Structure Metadata:
   INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  268724.500, 7485552.500) ( 47d15' 6.30"W, 22d43'17.44"S)
Lower Left  (  268724.500, 7447502.500) ( 47d15'26.74"W, 23d 3'53.89"S)
Upper Right (  314093.500, 7485552.500) ( 46d48'36.78"W, 22d43'37.63"S)
Lower Right (  314093.500, 7447502.500) ( 46d48'53.22"W, 23d 4'14.43"S)
Center      (  291409.000, 7466527.500) ( 47d 2' 0.78"W, 22d53'46.41"S)
Band 1 Block=45369x1 Type=Float32, ColorInterp=Gray
   NoData Value=-32768
   Overviews: 22685x19025, 11343x9513, 5672x4757, 2836x2379


Eduardo Patto Kanegae
http://www.webmapit.com.br | @webmapit


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