Adjusting raster images on-the-fly?

[Frank Warmerdam]

Rahkonen Jukka wrote:
> Hi,
> 
> We have whole a lot of colour infrared aerial (CIR) photos and users
> from two different organisations. Both organisations would use the
> imagery adjusted in the way they have been used to and with CIR photos
> this means two totally different appearance from the same original
> imagery, reddish or greenish. Because of this we have been forced to
> have two separate physical image sets processed with different settings.
> 
> Now I wonder if there might be some way to do this server side with
> MapServer. If we could do something similar to applying an adjustment
> layer "Curves" in Photoshop before sending the image through WMS service
> we would be able to save some 5 terabytes of disk space. In a similar
> way it would be often good for our imagery to push it through something
> like unsharp mask filter.
> 
> Has anybody done or seen something like this? I do know of new ESRI
> ArcGIS Image Server but not anything else. I believe I could address one
> programmer to work on this if someone could point us where to start.

Jukka,

I think this would be relatively easy to incorporate.  You could either
insert it in the LoadGDALImage() function in mapdrawgdal.c, or shortly after
it is called in msDrawRasterLayerGDAL().  The scaling implementation in
LoadGDALImage() may give you a good model to work from.

If you are just wanting to maintain this as a local hack to your MapServer
you can just go ahead and do it.  If you would like to approach this as a
general feature to be incorporated back into the core mapserver then an
RFC should be prepared describing the implementation you propose.

If you would like, I could also implement such a feature on contract
though that isn't really necessary given that you have programmers of your
own.  In any event, I'd be willing to provide some advice and answer a few
questions as needed.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | President OSGeo, http://osgeo.org