Add ST_SimplifyVW

git-svn-id: http://svn.osgeo.org/postgis/trunk@13418 b70326c6-7e19-0410-871a-916f4a2858ee

diff --git a/doc/reference_processing.xml b/doc/reference_processing.xml
index b747e3d590f817b02fb6f34b061c5b3d9146e347..8ded1792dca37b606228aae4815b6ab313ebe6b7 100644 (file)
--- a/doc/reference_processing.xml
+++ b/doc/reference_processing.xml
@@ -2737,7 +2737,55 @@ FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As the_geom) As foo;
                  </refsection>
        </refentry>
 
-       <refentry id="ST_SetEffectiveArea">
+<refentry id="ST_SimplifyVW">
+         <refnamediv>
+               <refname>ST_SimplifyVW</refname>
+               <refpurpose>Returns a "simplified" version of the given geometry using the Visvalingam-Whyatt algorithm</refpurpose>
+         </refnamediv>
+
+         <refsynopsisdiv>
+               <funcsynopsis>
+                 <funcprototype>
+                       <funcdef>geometry <function>ST_SimplifyVW</function></funcdef>
+                       <paramdef><type>geometry</type> <parameter>geomA</parameter></paramdef>
+                       <paramdef><type>float</type> <parameter>tolerance</parameter></paramdef>
+                 </funcprototype>
+               </funcsynopsis>
+         </refsynopsisdiv>
+
+         <refsection>
+               <title>Description</title>
+               <para> Returns a "simplified" version of the given geometry using the Visvalingam-Whyatt algorithm. 
+               Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry. 
+               Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.</para>
+
+               <note><para>Note that returned geometry might loose its
+                               simplicity (see <xref linkend="ST_IsSimple" />)</para></note>
+               <note><para>Note topology may not be preserved and may result in invalid geometries.  Use  (see <xref linkend="ST_SimplifyPreserveTopology" />) to preserve topology.</para></note>
+               <note><para>This function handles 3D and the third dimmension will affect the result</para></note>
+               <para>Availability: 2.2.0</para>
+         </refsection>
+
+                 <refsection>
+                       <title>Examples</title>
+                       <para>A linestring that get the efffective area calculated. All points is returned since we give 0 as themin area threashold</para>
+                               <programlisting>
+
+select ST_AStext(ST_SimplifyVW(geom,30)) simplified
+FROM (SELECT  'LINESTRING(5 2, 3 8, 6 20, 7 25, 10 10)'::geometry geom) As foo; 
+-result
+ simplified
+-----------+-------------------+
+LINESTRING(5 2,7 25,10 10)
+
+                               </programlisting>
+                 </refsection>
+                 <refsection>
+                       <title>See Also</title>
+                       <para><xref linkend="ST_SetEffectiveArea" />, <xref linkend="ST_Simplify" />, <xref linkend="ST_SimplifyPreserveTopology" />, Topology <xref linkend="TP_ST_Simplify"/></para>
+                 </refsection>
+       </refentry>
+               <refentry id="ST_SetEffectiveArea">
          <refnamediv>
                <refname>ST_SetEffectiveArea</refname>
                <refpurpose>Sets for each vertex point it's effective area,  
@@ -2750,32 +2798,34 @@ FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As the_geom) As foo;
                        <funcdef>geometry <function>ST_SetEffectiveArea</function></funcdef>
                        <paramdef><type>geometry</type> <parameter>geomA</parameter></paramdef>
                        <paramdef><type>float</type> <parameter>threashold = 0</parameter></paramdef>
+                       <paramdef><type>integer</type> <parameter>set_area = 1</parameter></paramdef>
                  </funcprototype>
                </funcsynopsis>
          </refsynopsisdiv>
 
          <refsection>
                <title>Description</title>
-               <para> Sets for each vertex point it's effective area from Visvalingam’s algorithm.
+               <para> Sets for each vertex point it's effective area from Visvalingam-Whyatt’s algorithm.
                        The effective area is stored as the M-value of the geomtries. 
-                       If the second optional parameter is used, the resulting geometriy will be build obnly on vertex points with an effective area 
+                       If the second optional parameter is used, the resulting geometriy will be build only on vertex points with an effective area 
                        greater than or equal to that threashold value. That will be a simplified geometry.
-                       
+                       </para><para>
                        This function can be used for server side simplification by using the threashold. Another option is to not give any threashold value. 
                        Then you get the full geometry back, but with effective areas as M-values wich can be used by the client to simplify very fast.
-                       
+                       </para><para>
                        Will actually do something only with
                        (multi)lines and (multi)polygons but you can safely call it with
                        any kind of geometry. Since simplification occurs on a
                        object-by-object basis you can also feed a GeometryCollection to
                        this function.
+                       </para>
                        
-                       This function handles 3D and the third dimmension will affect the effective area.</para>
 
                <note><para>Note that returned geometry might loose its
                                simplicity (see <xref linkend="ST_IsSimple" />)</para></note>
                <note><para>Note topology may not be preserved and may result in invalid geometries.  Use  (see <xref linkend="ST_SimplifyPreserveTopology" />) to preserve topology.</para></note>
                <note><para>The output geoemtry will loose all previous information in the M-values</para></note>
+               <note><para>This function handles 3D and the third dimmension will affect the effective area</para></note>
                <para>Availability: 2.2.0</para>
          </refsection>
 
@@ -2789,13 +2839,13 @@ FROM (SELECT  'LINESTRING(5 2, 3 8, 6 20, 7 25, 10 10)'::geometry geom) As foo;
 -result
  all_pts | thrshld_30
 -----------+-------------------+
-LINESTRING M (5 2 1.79769313486232e+308,3 8 29,6 20 1.5,7 25 49.5,10 10 1.79769313486232e+308) | LINESTRING M (5 2 1.79769313486232e+308,7 25 49.5,10 10 1.79769313486232e+308)
+LINESTRING M (5 2 3.40282346638529e+38,3 8 29,6 20 1.5,7 25 49.5,10 10 3.40282346638529e+38) | LINESTRING M (5 2 3.40282346638529e+38,7 25 49.5,10 10 3.40282346638529e+38)
 
                                </programlisting>
                  </refsection>
                  <refsection>
                        <title>See Also</title>
-                       <para><xref linkend="ST_Simplify" />, <xref linkend="ST_SimplifyPreserveTopology" />, Topology <xref linkend="TP_ST_Simplify"/></para>
+                       <para><xref linkend="ST_SimplifyVW" /></para>
                  </refsection>
        </refentry>
        

diff --git a/postgis/postgis.sql.in b/postgis/postgis.sql.in
index bd52d2a6d708a4f0190a0c3041665f9ab9e6cae3..bd1758ff5b85fd84424f9e0902334e80ec990183 100644 (file)
--- a/postgis/postgis.sql.in
+++ b/postgis/postgis.sql.in
@@ -2910,7 +2910,13 @@ CREATE OR REPLACE FUNCTION ST_Simplify(geometry, float8)
        LANGUAGE 'c' IMMUTABLE STRICT;
        
 -- Availability: 2.2.0
-CREATE OR REPLACE FUNCTION ST_SetEffectiveArea(geometry,  float8 default 0)
+CREATE OR REPLACE FUNCTION ST_SimplifyVW(geometry,  float8)
+       RETURNS geometry
+       AS 'MODULE_PATHNAME', 'LWGEOM_SetEffectiveArea'
+       LANGUAGE 'c' IMMUTABLE STRICT;
+       
+-- Availability: 2.2.0
+CREATE OR REPLACE FUNCTION ST_SetEffectiveArea(geometry,  float8 default 0, integer default 1)
        RETURNS geometry
        AS 'MODULE_PATHNAME', 'LWGEOM_SetEffectiveArea'
        LANGUAGE 'c' IMMUTABLE STRICT;