[gdal-dev] MapServer's image quality stinks serving up these NOAA NRCs

[Christopher Barker]

Vincent Schut wrote:
> but my first guess 
> would be: don't use palette images, use rgb or rgba.

Yes, I think this is the issue too. If you re-scale or warp or 
interpolate palleted images, GDAL uses nearest neighbor interpolation, 
which gets pretty ugly with images like the RNCs.

> You can control 
> this with a mapserver output file format parameter,

I don't know what your rendering stack looks like, but it may not be 
that simple. What you need to do is make sure that the RNCs are 
converted to RBG BEFORE they are altered in any other way -- then all 
warping, re-scaling, etc can be done with a better interpolation scheme. 
I suspect you'll need to convert them, store them on disk that way, so 
that what MapServer is seeing is the RGB versions.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
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Chris.Barker at noaa.gov