[GRASS-user] Making images colours uniform

[Nikos Alexandris]

Daniel Victoria wrote:
> I never used it but I believe there is an addon I.hist.match for histogram
> matching

Yes, it's i.histo.match for grass70:
<https://svn.geotools.org/grass/grass-
addons/grass7/imagery/i.histo.match/i.histo.match.html>

A related thread:
<http://lists.osgeo.org/pipermail/grass-dev/2013-February/062157.html>.

It works, with integer values and doesn't like the "." character in the name 
of the input raster maps (currently?).

Note, however, histogram matching wont "work" always, i.e. wont bring always 
eye-pleasant results.  Normalising observations (read pixel values) of 
different acquisitions (to a common reference) from the same sensor (as I 
understand in this case), depends on many things (the acquisition geometry 
itself, the illumination and atmospheric conditions at the time of the 
acquisition, and other parameters).

It is however, in a sense, "required" if one needs to not only visually 
interpret a mosaic, but also in case of attempting to cluster/segment/classify 
an image(-mosaic).

[rest deleted]

Best, Nikos
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