[postgis-users] Pixels' neighbors

dustymugs dustymugs at gmail.com
Tue Jul 2 13:48:36 PDT 2013


ST_MapAlgebraNgb definitely cannot help resolve neighboring tiles.

-bborie

On 07/02/2013 01:33 PM, Hugues François wrote:
> Hello Bborie,
> 
> Thanks for your answers.  I have requested  our team to migrate to postgis2.1 since beta version been released but unsuccessfully. I hope things will move with the official release. I fall in love with these "new sexy features" and others.
> 
> Awaiting for this moment, I will look further at st_MapAlgebraNbr but I'm afraid I won't manage to deal with different tiles.
> 
> Regards,
> 
> Hugues
> 
> -----Message d'origine-----
> De : postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-bounces at lists.osgeo.org] De la part de dustymugs
> Envoyé : mardi 2 juillet 2013 19:09
> À : postgis-users at lists.osgeo.org
> Objet : Re: [postgis-users] Pixels' neighbors
> 
> 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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