[mapserver-users] SCALE=AUTO applied to current view or entire layer?

[John Maurer]

Dear MapServer users,
When applying the PROCESSING directive "SCALE=AUTO" to a RASTER layer in 
MapServer, I was hoping this would apply a suitable contrast stretch for 
the currently selected spatial extent of the layer. But it seems that 
the contrast stretch is being applied to the entire layer regardless of 
where I am zoomed into. This means for a file with a large dynamic range 
that when zooming in to some areas, the contrast stretch is quite 
horrible (e.g. mostly gray tones or mostly dark tones or mostly light 
tones). My laborious workaround has been to create separate layers for 
the same raster data file with separate contrast stretches ranging from 
ultra-high contrast to ultra-low contrast using different 
"SCALE=min,max" settings. Is there a better way?? What is needed is a 
way for MapServer to apply an automatic contrast stretch to the current 
map view for the selected raster layer. You can get this kind of feature 
in many image processing applications (e.g. ENVI) so it would be 
fantastic to have this in MapServer as well. Thanks for any help!
Cheers,
John Maurer

-- 
John Maurer
Web/Database Applications Engineer
National Snow and Ice Data Center (NSIDC)
University of Colorado at Boulder
http://cires.colorado.edu/~maurerj
+1-303-586-1677
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"Without geography, you're nowhere!"