[mapserver-users] mapserver palette color

[jorgelopez]

Hello everyone:

I am trying to serve tiff images with mapserver by using mapserver v.5.6.5
with WCS implemented protocol v.1.0.0. All is fine in the sense that
three-band raster are served correctly with a WCS client (RGB composite
renderer with ArcMap, for instance). BUT if I want to display a single band
raster with a palette color describing some (discrete) categories, for
instance, a thematic raster layer (Corine -- Use and Land covers), the
connection to WCS server by using WCS client is fine, but the image is
served like a continuos band range instead a discrete colors as
corresponding to color table. So my WCS client is not detecting inherent
properties in the raster data. 

So, at this point I have some doubts:  
*my mapfile is not well defined
*the protocol does not support this and is not suited to serve discrete
(unique) values
*I am ignorant about how is rendered images with Mapserver 


Maybe third part is the correct statement. As far as I know built-in libs
and GDAL is responsible for rendering raster in Mapsserver. My CGI bin is
compiled with GDAL support, so raster will be managed by it;  gdalinfo
<filename> gives me information about raster layer (land cover) showing a
color table with a single band and 255 entries (only 13 categories with
different colours). Questions that throw some light for me because I have
not found clear directions in docs. 

I dont know if I have to specify CLASS definition for pixels that indicates
classification of pixels in raster (like in ref
http://mapserver.org/input/raster.html#how-are-rasters-added-to-a-map-file)
could be tedious and I didn´t get it. 


- I have defined OUTPUTFORMAT object in my mapfile like this: 

  OUTPUTFORMAT
    NAME 'GEOTIFF'
    DRIVER "GDAL/GTiff"
    MIMETYPE "image/tiff"
#  IMAGEMODE 'INT16'
#  IMAGEMODE 'PC256'   
    IMAGEMODE 'BYTE'
    EXTENSION 'tif'
  END   #end BANDS

but by using IMAGEMODE  'BYTE' it is rendered like a single-band image with
a greyscale (continuous but not discrete). In docs
(http://mapserver.org/ogc/wcs_format.html) I have read that IMAGEMODE
'PC256'  is needed to serve images with a color table and one single band. 

- I ignore PROCESSING directive. I dont know if a I should to indicate that
how to partitioning band like this 

	PROCESSING "SCALE=0,255"
	PROCESSING "SCALE_BUCKETS=XXX"

to obtain a color table as raster definition. 

- 'wcs_band_count' '1' 
  'wcs_nativeformat'  '8-bit GeoTIF' 

Does anyone know how to indicate mapserver to serve raster as 'raw data' ?

Some trends how to do it and getting out with this are wellcome. 

Jorge



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