[GRASS-user] "Select shapes from image"[->Gimp]/tracing in GRASS ?

GRASS GRASS user
1

Hi,

can the following "semi-interactive edge tracing on raster" task be realized using the current GRASS modules ?

* Data: A raster map (think: Landsat RGB, Corinne landcover or alike)
* Input: The user provides two points, both being located on/near a border between two areas in the raster map (entered via the GUI).
* Task: "Some combination of GRASS modules" derives a shortest path (a subset of pixels, not a vector) between the two given points which is plotted along the contrast changes of the raster data.

In Gimp, a similar functionality goes by the name "Select shapes from image".

Can we do such a task with GRASS ?

Peter

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Dr. Peter Löwe
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2

Hi Peter!

peter:
...

* Task: "Some combination of GRASS modules" derives a shortest path (a
subset of pixels, not a vector) between the two given points which is
plotted along the contrast changes of the raster data.

There is i.zc and I think r.gauss (an add-on provided by Jachym [1])
that should do edge-detection. Haven't used i.zc, with r.gauss I was
playing a bit in the past.

Cheers, Nikos
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[1] http://grass.osgeo.org/wiki/GRASS_AddOns#r.gauss