[Gdal-dev] LUT colour correction to GDAL

[Frank Warmerdam]

Rahkonen Jukka wrote:
> What I might want to do is to colour correct the original images by
> creating just external LUT tables for them in text format. Next I would
> like to mosaic the original images directly to the final, colour
> corrected target file with just nominal computional extra cost by
> runnign them through gdalwarp with '-wo LUT_COLOR_CORRECTION=YES' option
> set :)
> 
> In my case I could create LUT tables manually. Perhaps some clever
> programmer could even integrate the creation on LUT tables for usual
> tasks, like linear or standard deviation stretch, into some program that
> counts histograms?  For more sophisticated adjustments an external tool
> like GIMP showing preview of the result would be nice.

Jukka,

The gdalenhance can scale and apply a LUT.  It supports a LUT configuration
file that looks like this:

1:Band -0.5:ScaleMin 255.5:ScaleMax 0 0 0 0 0 0 0 0 2 4 4 4 ... 255

I have attached the literal config file example.  The config file may
contain multiple bands (each on their own line) though this example is
for a single band.  It can be applied like:

  gdalenhance -config x.config -ot Byte in.tif out.tif

The gdalenhance utility currently only exists in GDAL trunk (aka 1.5)
and is far from doing everything I had intended for it.  But with some
scripting to prepare the LUTs it should be suitable to preprocess your
imagery.

I'm not too inclined to incorporate application of LUT files in gdalwarp.

I would also like to mention that GRASS includes a variety of tools for this
sort of application.  And that OSSIM also apparently includes an excellent
color balancing and mosaicing capability that might be ideal for this sort of
use though I don't have personal experience with it.

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    | President OSGeo, http://osgeo.org

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