[postgis-devel] Another idea to speedup raster value editing

[Paul Ramsey]

Kinda... but then you've got a multipoint to deal with and that's
easier because...?
How about just getting/taking an array?
P.

On Wed, Feb 1, 2012 at 12:52 AM, Sandro Santilli <strk at keybit.net> wrote:
> I've been thinking that for my use case (create the NTv2 gridshift)
> it would be fast to pass a measured MULTIPOINT geometry where X/Y
> would address the pixel and M would set the value.
>
> The same representation could be useful in output, to use in place
> of ST_PixelAsPolygon.
>
> Such function, implemented in C, would allow to set and get all values in
> a band with a single raster deserialization.
>
> Map algebra, btw, you could perform on the M values directly.
> Something like:
>
>  WITH
>  pixels AS (
>    SELECT (ST_DumpPixelsAsPointM(rast)).geom FROM myrasttable
>  ),
>  newpixels AS (
>    SELECT ST_Point(ST_X(geom),ST_Y(geom), ST_M(geom)+1) as geom
>  )
>  SELECT ST_SetValueFromPointM(rast, st_collect(geom) FROM newpixels;
>
> How do you like it ?
>
> --strk;
>
>  ,------o-.
>  |   __/  |    Thank you for PostGIS-2.0 Topology !
>  |  / 2.0 |    http://www.pledgebank.com/postgistopology
>  `-o------'
>
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