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

[Sandro Santilli]

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;

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