Changes between Version 121 and Version 122 of WKTRaster/SpecificationWorking01

Timestamp:

Apr 14, 2010, 10:48:12 AM (14 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking01

@@ -244 +244 @@
  This function could be roughly implemented as a SQL function looking like 'SELECT ST_Collect((ST_DumpAsPolygons(raster)).geom)'. For sure a more specialised version could be faster than ST_AsPolygon.
 
-'''ST_DumpAsPolygons(raster, integer) -> geomval set''' - Returns a set of "geomval" value, one for each group of pixel sharing the same value for the provided band.
-
- This is a set-returning function (SRF). A "geomval" value is a complex type composed of a polygon geometry (one for each group of pixel sharing the same value) and the value associated with this geometry. These values are always returned as a value of type double precision. The shape of each polygon follow pixels edges.
+'''ST_DumpAsPolygons(raster, integer) -> geomval set''' - Returns a set of "geomval" value, one for each contiguous group of pixel sharing the same value for the provided band.
+
+ This is a set-returning function (SRF). A "geomval" value is a complex type composed of a polygon geometry (one for each contiguous group of pixel sharing the same value) and the value associated with this geometry. These values are always returned as a value of type double precision. The shape of each polygon follow pixels edges.
 
  Variant 1: ST_DumpAsPolygons(raster) -> geomval set -- default to band # 1
@@ -255 +255 @@
  
  This function is at the base of the first version of ST_Intersection which compute the intersection between a raster and a geometry.
-
- The "CONTIGUOUS" version could be implemented by "dumping" (see geometry_dump in PostGIS) the complex polygon into separate simple polygons.
 
  To avoid linking directly with PostGIS (see "Why avoid to link with PostGIS?" below) It should be implemented as a SQL wrapper around DumpAsWKTPolygons() looking something like this: