Changes between Version 76 and Version 77 of WKTRaster/SpecificationWorking01

Timestamp:

Dec 17, 2009, 12:57:13 PM (14 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking01

@@ -259 +259 @@
  '''Implementation details'''
  
- This function construct the WKT strings representing the geometries grouping pixels of a raster having the same value. It does not directly construct geometries and therefore prevent WKT Raster from having to link with liblwgeom.a (see "Why avoid to link with PostGIS?" below)
+ This function construct the WKT strings representing the geometries grouping pixels of a raster having the same value. It does not directly construct geometries and therefore prevent WKT Raster from having to link with liblwgeom.a (see "Why avoid to link with PostGIS?" below) It should also return the value associated with this WKT polygon.
+
+ Ways to return 2 values from a function:
+
+ Functions with Output Parameters
+
+ CREATE FUNCTION sum_n_product (x int, y int, OUT sum int, OUT product int)[[BR]]
+ AS 'SELECT $1 + $2, $1 * $2'[[BR]]
+ LANGUAGE SQL;
+
 
  It should be implemented by passing the raster to GDAL and convert each polygon produced by the [http://www.gdal.org/gdal__alg_8h.html GDALPolygonize function] to a WKT string.