[gdal-dev] Using VRT images with derived bands (pixel function) with MapServer

[Armin Burger]

Dear all

I would be interested in using VRT images with "derived bands" as 
described on the VRT image documentation page. This requires the 
definition of a pixel function and the registration of this function in 
the used application via "GDALAddDerivedBandPixelFunc".

The provided sample function is already towards what I'm looking for. I 
would just need to adapt it accordingly (calculating band 1 as 
combination of source band 1 and 3).

Since my main interest is to use such image definition in the context of 
Mapserver, my question is if there could be a way to use this also from 
Mapserver as application? If yes, where would I need to register the 
function and how would I best make the function available to Mapserver 
(maybe via an .o file that is created when compiling)? Maybe somewhere 
inside mapgdal.c ?

Would such a pixel function be used also in case when not the full 
resolution image (i.e. TIFF file referenced in the VRT file) is read but 
one of the overviews from the .ovr file associated to the Tiff file?

Thanks in advance for any hints

Armin