[mapserver-users] fast resampling, and RGB support

[Frank Warmerdam]

Folks, 

I have updated the MapServer support for resampling rasters (a 3.5 feature,
found only in CVS) to use a fast approximation for the coordinate system
transformation as appropriate.  

I have also added prototype support for RGB (ie. 24bit) source images through
the GDAL interface.  These files are boiled down through a static 5x7x5 
color cube on output.  While this ensures things remain relatively fast, the
resulting 8 bit images can be pretty poor representation of the original 24bit
image depending on the nature of the image being displayed.  This is intended
to just be a quick and dirty hack for people who want to publish 24bit data
without having to reprocess it into eight bit offline.  However, to produce
good results it is vastly preferable to preprocess RGB images by computing
an optimal colormap, and using dithering when converting from 24bit to 8bit. 
There are GDAL tools to accomplish this if people need to use them. 

In the future MapServer may be altered to allow generation of 24bit output
rendering this issue relatively moot, but that won't be 3.5 as far as I know.

Anyone interested in testing the RGB or fast resampling for rasters can 
build from CVS, and contact me if they have any problems. 

Best regards,

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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent