[GRASS-dev] Image Segmentation - Summer of Code

[Eric Momsen]

On Thu, Sep 6, 2012 at 8:59 AM, Moritz Lennert <mlennert at club.worldonline.be
> wrote:

> On 06/09/12 15:44, Markus Neteler wrote:
>
>> Hi Eric,
>>
>>
>> great work with the i.segment, I just made a test with the NC Landsat
>> sample data:
>>
>> i.segment -w -l group=lsat7_2000 output=testsegment threshold=4 \
>>                 method=region_growing similarity=euclidean minsize=20
>>
>> The result looks already pretty nice without further parameter tuning.
>>
>> It would now be cool to susequently perform a unsupervised classification
>> with, say, i.cluster/i.maxlik in order to group the segments to a certain
>> number of classes.
>>
>> Would that be feasible from the resulting image statistics?
>>
>
> I'm not sure that i.cluster is the right tool here. I think it might be
> more efficient / easier to actually transform the segments into vectors and
> fill up the attribute table with a whole series of statistics concerning
> spectral, shape, context, etc characteristics of these segments.
>
> I guess you could also create a whole series of new bands, one for each of
> the characteristics mentioned above, in which for each pixel you put the
> statistic of its segment concering the respective characteristic, and
> submit that to i.cluster. But somehow that doesn't sound as efficient to
> me...
>
> Moritz
>

It is nice to hear more people are trying out i.segment!

This week I updated my local copy of r.univar to include number of segments
as the last column of the output table.  Just a quick hack, if it were to
be considered to be added in there are definitely some error checking, etc
that should be added too.  I started there because of the zone
functionality in r.univar: I could use the segment results as the zone map
(and input as the single raster map I had segmented) and then r.univar
could find statistics for each segment.

I'm not familiar (yet) with i.cluster/i.maxlik to be able to comment on
that part.  I'm certainly interested to hear the most pressing needs for
using the outputs from i.segment, and if some updates like that should be
polished a bit more to be considered for everyone.

(I need to run to a meeting, if there is interest in what I did to r.univar
I can send it out later.)

-Eric
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