Feature request: n-band raster layer classification

[Vincent Schut]

Hello mapserver-developers,

In the near future, we are going to need raster layer classes based on
more than just the first band of a raster layer. 'We' means the small
company I'm working for, SarVision (www.sarvision.nl). We mainly develop
automated systems for tropical forest monitoring using satellite imagery
from several sensors, optical as well as radar. Besides that we offer
our customers/partners webgis access to the results through mapserver
and a dedicated webgis client.

One of our partners would like to be able to show a layer which is
actually a combination of 2 or more raster layers. As an example: show
all pixels that have an altitude of more than 500m or that are steeper
than 20 degrees in red, the rest in green. Now this is still one of the
simpler examples, and one of the prerequisites is that the
classification values (500m and 20degrees) are dynamically adjustable by
the user. I've been thinking of several workarounds for this, but of
course the most suitable way would be to implement raster classes based
on [band1], [band2], etc. instead of [pixel]. However, I'm afraid I
don't have the skills to implement this.

Could someone who is more knowledgeable on mapserver hacking elaborate a
bit on the feasibility of this enhancement? Would it be fairly trivial
to implement this, or almost impossible? Depending on our partner's
budget (which we don't know yet) we might even be able to sponsor the
implementation of this enhancement.

Regards,

Vincent Schut.