[postgis-users] ST_Clip

[Pierre Racine]

Now what if you symbolize the value of the raster properly (1 = white and -1 = black) to display the shape of the buffer?

> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
> bounces at postgis.refractions.net] On Behalf Of Paolo Cavallini
> Sent: Thursday, July 26, 2012 2:04 PM
> To: postgis-users at postgis.refractions.net
> Subject: Re: [postgis-users] ST_Clip
> 
> Il 26/07/2012 19:54, Paolo Cavallini ha scritto:
> > Il 26/07/2012 19:39, Pierre Racine ha scritto:
> >> What happen if do a query like this:
> >>
> >> SELECT (gv).geom, (gv).val
> >> FROM (SELECT
> ST_PixelAsPolygons(ST_AsRaster(ST_Buffer(ST_Centroid(ST_Envelope(rast)),
> 0.5000), rast, ST_BandPixelType(rast, 1), 1, -1)) gv
> >>       FROM hdr
> >>       WHERE rid = 4
> >> ) foo
> >>
> >> and display the resulting geometries labelled with the values?
> >>
> >> This is the first step of the clipping: creating a rasterized version of the buffer
> geometry aligned on the raster.
> If I redo the query with the same buffer size as my previous one, I
> obtain a grid that encloses exactly the buffer; the raster is smaller.
> See attached.
> Thanks.
> 
> --
> Paolo Cavallini - Faunalia
> www.faunalia.eu
> Full contact details at www.faunalia.eu/pc
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