[Mapserver-users] Smoothing NEXRAD imagery

[Daryl Herzmann]

Frank and others,

Thanks for your helpful response.  I am not a very good c-programmer, so I 
really appologize in advance for my ignorance.

Do nearest neighbour and cubic convolution code exist in GDAL?

I tell you all what, smoothing images would rock for many other purposes 
than NEXRAD data. :)

Thanks,
 Daryl

On Tue, 28 Jan 2003, Frank Warmerdam wrote:

>Daryl Herzmann wrote:
>> I have been working on generating maps of current NEXRAD (Weather 
>> Service RARAR) imagery and overlaying observations.  This is currently 
>> working great, except the pixelation that occurs at very close range.  
>> Does anyone know how to implement an automatic TIFF smoothing algorithm at 
>> close ranges?
>> 
>> Here is a page with an example of what happens to the NEXRAD image at 
>> close ranges...  The pixelation at 25km is not that bad and will probably 
>> be what I live with for the final app.
>
>Daryl,
>
>If you are using MapServer 3.7 from CVS there is a LoadGDALImage() function
>in mapdrawgdal.c that is responsible for most imagery loads from GDAL. It
>would be relatively easy to add a processing option to the map file that
>would direct this function to load oversampled imagery with some sort of
>smoothing - nearest neighbour or cubic convolution for instance.
>
>If you are feeling ambitious go ahead and take a crack at it.  The processing
>arguments are generic all your changes would be in this one function.
>
>The special case to watch for would be when src_xsize > dst_xsize or
>src_ysize > dst_ysize.  Just modify the code to loading into a data array
>at the source resolution and resample appropriate into the output buffer.
>
>I could do this, but I have little time available.  Of course if you wanted
>to pay I am sure someone would be happy to do it.
>
>Best regards,
>
>

-- 
/**
 * Daryl Herzmann (akrherz at iastate.edu)
 * Program Assistant -- Iowa Environmental Mesonet
 * http://mesonet.agron.iastate.edu
 */