[Mapserver-users] Help COLOR_MATCH_THRESHOLD

[Jan Hartmann]

Another great feature! Works great for individual raster maps. With 
raster tiles everything works OK when zooming in into indivdual tiles, 
but with maps consisting of several tiles seams show up between the 
tiles. Is this resampling done differently for each tile?

Jan

Frank Warmerdam wrote:

> By default the GDAL raster input code for MapServer will just truncate 
> pixel
> values outside the range 0-255, so any elevation over 255 would be set to
> 255.
> 
> What you need to do is establish the range of values that can occur, and 
> then
> set a SCALING processing directive to control the scaling of the raw raster
> values into the 0-255 range.
> 
> For instance if a utility like gdalinfo (or metadata) tells you that the
> range of elevation is 0 to 1000 you might put the following directive in
> the LAYER section to force the input range to be scaled down to 0-255:
> 
>  PROCESSING "SCALE=0,1000"
> 
> If you don't want to figure out the min and max for your dataset, and don't
> need to be able to document exactly what output values correspond to in
> input elevations you could just use auto-scaling.
> 
>  PROCESSING "SCALE=AUTO"
> 
> Note that auto-scaling is based only on the rectangle of raster data loaded
> for a particular request, so the scaling applied will vary depending on the
> section of data being viewed.  This is often inappropriate.  
> Auto-scaling will
> always be inappopriate if you want to produce a legend with meaningful 
> range
> values for the classes.
> 
> I think that the SCALE processing option is documented in the mapfile
> reference.
> 
> Best regards,
>