[postgis-users] Pixels' neighbors

[dustymugs]

Hugues,

Another possibility if you have PostGIS 2.1 is ST_Neighborhood().

http://www.postgis.net/docs/manual-dev/RT_ST_Neighborhood.html

-bborie

On 07/02/2013 09:47 AM, Hugues François wrote:
> Hello,
> 
> Given a one band raster made of numerous tiles and a point geometry from which I select one pixel, I would like to compare its value with its (8) neighbors' values. For now I do that with st_value(rast, geom) and playing with point coordinates (x +/- pixel width and y +/- height) : it works fine but it is very slow and I have to make a loop to compare selected pixels' values with their neighbors until I reach a certain value.
> 
> What I would like is to do all that only with raster but I don't see how to compare one pixel value with its neighbors (within the same tile or into a  neighbor tile). I assume I miss something and this is obvious for some of you, so if you could give a hand, i would be sincerely grateful.
> 
> Regards,
> 
> Hugues.
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