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|
----------------------------------------------------------------------
--
--
-- Copyright (c) 2009-2010 Pierre Racine <pierre.racine@sbf.ulaval.ca>
--
----------------------------------------------------------------------
-- NOTE: The ST_AsRaster() function is already implemented in C. This plpgsql script is provided only as an example.
-- Defining the plpgsql function below might overwrite the current C implementation and brake other functions dependent on it.
-- Use with caution.
CREATE OR REPLACE FUNCTION ST_AsRaster(geom geometry, rast raster, pixeltype text, nodatavalue float8, val float8)
RETURNS raster AS
$$
DECLARE
numband int := ST_NumBands(rast);
x1w float8 := ST_XMin(geom);
y1w float8 := ST_YMax(geom);
x2w float8 := ST_XMax(geom);
y2w float8 := ST_YMin(geom);
x1r int := ST_World2RasterCoordX(rast, x1w, y1w);
y1r int := ST_World2RasterCoordY(rast, x1w, y1w);
x2r int := ST_World2RasterCoordX(rast, x2w, y2w);
y2r int := ST_World2RasterCoordY(rast, x2w, y2w);
newx1w float8 := ST_Raster2WorldCoordX(rast, x1r, y1r);
newy1w float8 := ST_Raster2WorldCoordY(rast, x1r, y1r);
newwidth int := abs(x2r - x1r) + 1;
newheight int := abs(y2r - y1r) + 1;
newrast raster := ST_AddBand(ST_MakeEmptyRaster(newwidth, newheight, newx1w, newy1w, ST_ScaleX(rast), ST_ScaleY(rast), ST_SkewX(rast), ST_SkewY(rast), ST_SRID(rast)), pixeltype, nodatavalue, nodatavalue);
BEGIN
FOR x IN 1..newwidth LOOP
FOR y IN 1..newheight LOOP
IF ST_Intersects(geom, ST_Centroid(ST_PixelAsPolygon(newrast, x, y))) THEN
newrast := ST_SetValue(newrast, 1, x, y, val);
END IF;
END LOOP;
END LOOP;
RETURN newrast;
END;
$$
LANGUAGE 'plpgsql';
-- Test
SELECT (gv).geom, (gv).val
FROM (SELECT (ST_PixelAsPolygons(rast, 1)) gv
FROM (SELECT ST_AsRaster(the_geom, (SELECT rast FROM srtm_tiled_100x100 LIMIT 1), '8BSI', -1, 1) rast
FROM realcaribou_buffers_wgs
LIMIT 10) foo) foi
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