Changes between Version 79 and Version 80 of WKTRaster/SpecificationWorking01
- Timestamp:
- 12/18/09 12:48:03 (15 years ago)
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WKTRaster/SpecificationWorking01
v79 v80 239 239 '''ST_AsPolygon(raster) -> polygon geometry set''' - Returns a set of geometry, one for each group of pixel having the same value. 240 240 241 Th e shape of each polygon should exactly follow pixels edges.241 This is a set-returning function (SRF). The shape of each polygon should exactly follow pixels edges. 242 242 243 243 A ST_AsPolygon(raster, 'GROUP') variant should regroup every resulting polygon having the same value into complex (or multipart) polygons. … … 249 249 This function is at the base of the first version of ST_Intersection which compute the intersection between a raster and a geometry. 250 250 251 To avoid linking directly with PostGIS (see "Why avoid to link with PostGIS?" below) It should be implemented as a PL/pgSQL wrapper around ST_AsWKTPolygon() looking something like this: 252 253 FOR poly IN SELECT ST_GeomFromText(ST_AsWKTPolygon(rast)) FROM table LOOP 251 To avoid linking directly with PostGIS (see "Why avoid to link with PostGIS?" below) It should be implemented as a PL/pgSQL wrapper around ST_AsWKTPolygon() looking something like this: 252 253 CREATE TYPE raster_geom AS (value integer[], geom geometry); 254 255 256 FOR poly IN SELECT ST_GeomFromText(r.geom), FROM ST_AsWKTPolygon(rast) AS r LOOP 254 257 RETURN NEXT poly; 255 258 END LOOP;