[GRASS-user] Image segmentation

[Giuseppe Amatulli]

Thanks Markus,
the problem with the v.voronoi is that the polygon borders will be
calculate based on point distance and not on the cost surface.
Any other input?
Best
Giuseppe



On 19 January 2017 at 02:38, Markus Metz <markus.metz.giswork at gmail.com>
wrote:

>
>
> On Wed, Jan 18, 2017 at 8:16 PM, Giuseppe Amatulli <
> giuseppe.amatulli at gmail.com> wrote:
> >
> > Hi all,
> >
> > I would like to "segment" an image using a sort of Voronoi algorithm on
> a cost surface instead of distance between point.
> >
> > Below you can see an image where the black pixels identity areas with
> high cost value. I would like to identify the "valley" between theses black
> areas.
> >
> > In the second image I draft by hand an ideal solution for few high cost
> areas.
> >
> > Which grass command can do this kind of delineation?
>
> You can use v.voronoi: first extract the pixels with high cost values with
> e.g.
> r.mapcalc "high_cost = if(surface_map > threshold_value, 1, null())"
>
> Then convert to vector areas with
> r.to.vect input=high_cost output=high_cost type=area
>
> Now create Voronoi triangles for areas with
> v.voronoi input=high_cost output=high_cost_voronoi -a
>
> HTH,
>
> Markus M
> >
> > Thanks,
> >
> > Giuseppe
> >
> >
> >
> >
> >
> >
> > --
> > Giuseppe Amatulli, Ph.D.
> >
> > Research scientist at
> > Yale School of Forestry & Environmental Studies
> > Yale Center for Research Computing
> > Center for Science and Social Science Information
> > New Haven, 06511
> > Teaching: http://spatial-ecology.org
> > Work:  https://environment.yale.edu/profile/giuseppe-amatulli/
> >
> >
> >
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
>


-- 
Giuseppe Amatulli, Ph.D.

Research scientist at
Yale School of Forestry & Environmental Studies
Yale Center for Research Computing
Center for Science and Social Science Information
New Haven, 06511
Teaching: http://spatial-ecology.org
Work:  https://environment.yale.edu/profile/giuseppe-amatulli/
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