Changes between Version 100 and Version 101 of WKTRaster/SpecificationWorking01

Timestamp:

Jan 5, 2010, 2:47:30 PM (14 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking01

@@ -251 +251 @@
  This function is actually already implemented by the ST_raster_envelope() function which is wrongly named. There is also a ticket (#348) related to this function: http://trac.osgeo.org/postgis/ticket/348
 
-'''ST_Shape(raster) -> polygon geometry''' - Returns a geometry encomparsing every pixel having a significant value (different than the NODATA value).
+'''ST_Shape(raster, integer) -> polygon geometry''' - Returns a geometry encomparsing every pixel having a significant value (different than the NODATA value) for the provided band.
 
  This polygon geometry might contain holes if some internal areas of the raster contain pixels with NODATA values.
 
+ Variant 1: ST_Shape(raster) -> polygon geometry -- default to band # 1
+
  '''Implementation details'''
 
  This function could be roughly implemented as a SQL function looking like 'SELECT ST_Collect((ST_AsPolygon(raster)).geom)'. For sure a more specialised version could be faster than ST_AsPolygon.
 
-'''ST_AsPolygon(raster) -> geomval set''' - Returns a set of "geomval" value, one for each group of pixel sharing the same value.
+'''ST_AsPolygon(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.
 
+ Variant 1: ST_AsPolygon(raster) -> geomval set -- default to band # 1
+ Variant 2: ST_AsPolygon(raster, integer, 'UNGROUP')
+ Variant 3: ST_AsPolygon(raster, 'UNGROUP') -- default to band # 1
+
  This function should be used with precaution on raster with float pixel type as it could return one "geomval" (or polygon) per pixel. This kind of raster should be reclassified (using the planned ST_Reclassify(raster,...) function) before using ST_AsPolygon().
 
- '''Implementation details'''
- 
- A ST_AsPolygon(raster, 'REGROUP') variant should regroup every resulting polygon having the same value into complex (or multipart) polygons.
+ Variant 2 splits every resulting complex polygon sharing the same value into simple (or singlepart) polygons.
+
+ '''Implementation details'''
  
  This function is at the base of the first version of ST_Intersection which compute the intersection between a raster and a geometry.
@@ -290 +296 @@
 [[Image(WKTRasterAsPolygon.gif)]]
 
-'''ST_AsWKTPolygon(raster) -> wktgeomval set''' - Returns a set of "geomval" value, one for each group of pixel sharing the same value.
+'''ST_AsWKTPolygon(raster, band) -> wktgeomval 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 "wktgeomval " value is a complex type composed of a the wkt representation of a 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.
@@ -305 +311 @@
 
 
-'''ST_Intersects(raster, geometry) -> boolean''' - Returns TRUE if the geometry and the raster "spatially intersect" - (share any portion of space) and FALSE if they don't (they are Disjoint).
-
- Variant 1: ST_Intersects(geometry, raster) -> boolean
+'''ST_Intersects(raster, integer, geometry) -> boolean''' - Returns TRUE if the geometry and the raster "spatially intersect" - (share any portion of space) and FALSE if they don't (they are Disjoint).
+
+ Variant 1: ST_Intersects(geometry, raster, integer) -> boolean
+
+ Variant 2: ST_Intersects(geometry, raster) -> boolean -- default to band # 1
  
- Variant 2: ST_Intersects(raster, raster) -> boolean
+ Variant 3: ST_Intersects(raster, geometry) -> boolean -- default to band # 1
+
+ Variant 4: ST_Intersects(raster, raster) -> boolean
 
  This function permform a full intersection test and proceed in three steps to determine if the raster intersects with the geometry:
@@ -319 +329 @@
  3) If the second test returns TRUE, it checks if the geometry returned by ST_Shape(raster) intersects with the geometry. This test is slower since it involve the computation of the raster shape and it might involve the geometry shape.
 
- Variant 2 proceeds in a very similar way except that convex hulls of both rasters are computed and compared in step 2) and both shape of raster are computed and compared in step 3).
+ Variant 4 proceeds in a very similar way except that convex hulls of both rasters are computed and compared in step 2) and both shape of raster are computed and compared in step 3).
 
  If you want to limit the intersection test to the first condition, simply use the && operator. The raster and the geometry will be casted to their respective bounding box (box2d objects):
@@ -335 +345 @@
  It might be faster to skip test 2) if this test is not signicantly faster than test 3).
 
-'''ST_Intersection(raster, geometry) -> geometry''' - Returns a geometry that represents the shared portion of the geometry and the raster. 
+'''ST_Intersection(raster, integer, geometry) -> geometry''' - Returns a geometry that represents the shared portion of the geometry and the raster areas sharing a common meaningfull values. 
 
  Variant 1: 
 
-  ST_Intersection(geometry, raster) -> geometry
-
- Variant 2 & 3: 
-
-  ST_Intersection(raster, geometry, 'raster') -> raster[[BR]]
-  ST_Intersection(geometry, raster, 'raster') -> raster
-
- Variant 4 & 5: 
-
-  ST_Intersection(raster, raster) -> raster[[BR]]
-  ST_Intersection(raster, raster, 'geometry') -> geometry
+  ST_Intersection(raster, geometry) -> geometry -- default to band # 1[[BR]]
+  ST_Intersection(geometry, raster, integer) -> geometry[[BR]]
+  ST_Intersection(geometry, raster) -> geometry -- default to band # 1
+
+ Variant 2: 
+
+  ST_Intersection(raster, integer, geometry, 'raster') -> raster[[BR]]
+  ST_Intersection(raster, geometry, 'raster') -> raster -- default to band # 1
+
+ Variant 3: 
+
+  ST_Intersection(geometry, raster, integer, 'raster') -> raster[[BR]]
+  ST_Intersection(geometry, raster, 'raster') -> raster -- default to band # 1
+
+ Variant 4: 
+
+  ST_Intersection(raster, integer, raster, integer) -> raster[[BR]]
+  ST_Intersection(raster, raster) -> raster -- default to band # 1
+
+ Variant 5: 
+
+  ST_Intersection(raster, integer, raster, integer, 'geometry') -> geometry
+  ST_Intersection(raster, raster, 'geometry') -> geometry -- default to band # 1
 
  Returns a geometry that represents the point set intersection of the geometry and the raster. The raster is first polygonised using ST_AsPolygon(raster) and ST_Intersection(geometry, geometry) is then performed between the provided geometry and all the geometries resulting from the polygonisation of the raster.