legends for preclassified rasters

[bartvde@…]

Mapserver needs a way to produce legends for preclassified rasters. In my
opinion there are 2 options for this:

1. the option of a KEYIMAGE at the layer level (or maybe it should be called
LEGENDIMAGE in that case), in which a user can associate a LAYER with an already
present legend image for the classification present in his raster data

2. the option of having a "processing" directive in which you can say, don't use
this classification for the data itself, but only for generating the legend.
E.g. something like: CLASSIFICATION LEGENDONLY

Thoughts?

[bartvde@…]

E-mail from Frank 06-05-2005:

Folks,
 
There has been a desire by raster users to be able to have an entry
appear in legends for raster layers without having to force the raster
layer to be rendered using classification.  In the past having a class
on the raster would force the raster layer to be rendered using
classification rules, instead of it's inherent colors - but a class
was the only convenient way to have a layer appear in the legend. 
 
After discussion with Steve I have made a change in the GDAL 
based raster rendering to only use classification rules for rendering
if at least one class has a non-NULL expression.   So, it should be
no problem now to use a dummy class with a KEYIMAGE or other
mechanism to get a legend entry for a raster layer without classifying
it. 
 
This should become widely available in 4.6.0 beta2. 
 
Best regards,

[fwarmerdam]

I would add that bug 985 relates to this issue as well.