[GRASS-user] Making images colours uniform

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Hi all.
Is there a command in GRASS to merge adjacent images so that their colour tabel is
more uniform? I remember something, but cannot find it back.
All the best, and thanks.
- --
Paolo Cavallini - Faunalia
www.faunalia.eu
Full contact details at www.faunalia.eu/pc
Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
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On 26/03/13 17:59, Paolo Cavallini wrote:

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Hi all.
Is there a command in GRASS to merge adjacent images so that their colour tabel is
more uniform? I remember something, but cannot find it back.

I'm not sure if I completely understand what you are looking for, but does

r.colors raster=

do what you want ?

Moritz

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Il 27/03/2013 11:32, Moritz Lennert ha scritto:

I'm not sure if I completely understand what you are looking for, but does

r.colors raster=

do what you want ?

Sorry I was unclear. I have a series of ortophotos, each of them with a different
colour blend; when mosaicked, the result is ugly. My objective is to make them look
more similar.
Thanks.

- --
Paolo Cavallini - Faunalia
www.faunalia.eu
Full contact details at www.faunalia.eu/pc
Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
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I never used it but I believe there is an addon I.hist.match for histogram matching

On Mar 27, 2013 7:35 AM, “Paolo Cavallini” <cavallini@faunalia.it> wrote:

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Il 27/03/2013 11:32, Moritz Lennert ha scritto:

I’m not sure if I completely understand what you are looking for, but does

r.colors raster=

do what you want ?

Sorry I was unclear. I have a series of ortophotos, each of them with a different
colour blend; when mosaicked, the result is ugly. My objective is to make them look
more similar.
Thanks.


Paolo Cavallini - Faunalia
www.faunalia.eu
Full contact details at www.faunalia.eu/pc
Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
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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&gt;\.

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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Il 27/03/2013 13:53, Nikos Alexandris ha scritto:

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:

thanks a lot, will try.
all the best.
- --
Paolo Cavallini - Faunalia
www.faunalia.eu
Full contact details at www.faunalia.eu/pc
Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
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