WCS 2.0.1 single band RangeSubset writes out 3-band GeoTIFF

[jratike80]

With Mapserver 7.0.0 and with an attached mapfile, the following GetCoverage request that selects only one band with RangeSubset yields a 3-band GeoTIFF which only appears greyscale because the requested BandA is copied to all three bands.

http://localhost/cgi-bin/mapserv?map=wcs_demo_01.map&service=wcs&version=2.0.1&request=GetCoverage&coverageId=orthophotos&FORMAT=image/tiff&SUBSET=x(257000,258000)&SUBSET=y(6997000,6998000)&RangeSubset=BandA

Part of gdalinfo report from the "out.tif" file
Band 1 Block=2000x1 Type=Byte, ColorInterp=Red
Band 2 Block=2000x1 Type=Byte, ColorInterp=Green
Band 3 Block=2000x1 Type=Byte, ColorInterp=Blue

wcs_demo_01.txt

[jratike80]

More information:
This happens with the default GeoTIFF driver. The default driver has also another unwanted feature: it writes a RGB output from multi-band source like RGB-NIR 4-band imagery. It feels like the default IMAGEMODE is RGB even it is documented to be FLOAT32, and that the "wcs_imagemode" metadata item does not have any effect on the default image/tiff outputformat.

Single band / dual band / 4-band output is successful with a self-configured outputformat that sets the imagemode into BYTE.

OUTPUTFORMAT
  NAME GEOTIFF
  DRIVER "GDAL/GTiff"
  MIMETYPE "image/tiff"
  IMAGEMODE BYTE
  EXTENSION "tif"
END

For RBG-NIR imagery it seems also good to add this formatoption that prevents labeling the fourth band as alpha:

FORMATOPTION "ALPHA=UNSPECIFIED"

I wonder if it will be enough to improve the documentation or if the default GeoTIFF outputformat for WCS should be changed in the code. An out-of-the-box support for more than 3 bands would be convenient.

[sanfilippopablo]

@jratike80 Is it necessary to add the PROCESSING "BANDS=1,2,3,4" directive for it to output the 4 bands?

[Schpidi]

I added tests for this in #5566 hoping this was fixed recently as I can't reproduce. Please re-open if still valid.