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- Log -----------------------------------------------------------------
commit d9a245db5d8e41b2da1eaec9049bced6104fe418
Author: Martin Davis <mtnclimb at gmail.com>
Date: Thu Jun 9 16:21:06 2022 -0700
Doc for ST_SimplifyPolygonHull
diff --git a/doc/html/image_src/Makefile.in b/doc/html/image_src/Makefile.in
index c1eb3c7b3..1e943dd24 100644
--- a/doc/html/image_src/Makefile.in
+++ b/doc/html/image_src/Makefile.in
@@ -156,6 +156,8 @@ IMAGES= \
../images/st_split03.png \
../images/st_split04.png \
../images/st_simplifypolygonhull01.png \
+ ../images/st_simplifypolygonhull02.png \
+ ../images/st_simplifypolygonhull03.png \
../images/st_straightskeleton01.png \
../images/st_approximatemedialaxis01.png \
../images/st_subdivide01.png \
diff --git a/doc/html/image_src/st_simplifypolygonhull02.wkt b/doc/html/image_src/st_simplifypolygonhull02.wkt
new file mode 100644
index 000000000..58a0bacbc
--- /dev/null
+++ b/doc/html/image_src/st_simplifypolygonhull02.wkt
@@ -0,0 +1,2 @@
+ArgA-thin;POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))
+Result-thin;POLYGON ((161 165, 173 156, 186 144, 190 137, 185 131, 174 124, 166 119, 166 79, 158 57, 68 32, 40 31, 25 34, 17 41, 14 46, 11 57, 56 91, 33 97, 23 100, 22 107, 28 131, 80 135, 73 145, 85 157, 99 162, 122 170, 161 165))
diff --git a/doc/html/image_src/st_simplifypolygonhull03.wkt b/doc/html/image_src/st_simplifypolygonhull03.wkt
new file mode 100644
index 000000000..7566249b8
--- /dev/null
+++ b/doc/html/image_src/st_simplifypolygonhull03.wkt
@@ -0,0 +1,2 @@
+ArgA-thin;POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))
+Result-thin;POLYGON ((131 158, 116 158, 99 162, 89 137, 76 130, 59 127, 28 131, 46 116, 36 100, 64 94, 75 72, 41 68, 33 54, 68 32, 90 48, 112 53, 145 57, 158 57, 161 97, 158 115, 158 121, 190 137, 169 140, 179 148, 161 165, 131 158))
diff --git a/doc/reference_processing.xml b/doc/reference_processing.xml
index e4d422edb..65044124a 100644
--- a/doc/reference_processing.xml
+++ b/doc/reference_processing.xml
@@ -609,6 +609,60 @@ POINT(0.5 1)
</refsection>
</refentry>
+ <refentry id="ST_ChaikinSmoothing">
+ <refnamediv>
+ <refname>ST_ChaikinSmoothing</refname>
+ <refpurpose>Returns a smoothed version of a geometry, using the Chaikin algorithm</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>geometry <function>ST_ChaikinSmoothing</function></funcdef>
+ <paramdef><type>geometry</type> <parameter>geom</parameter></paramdef>
+ <paramdef><type>integer</type> <parameter>nIterations = 1</parameter></paramdef>
+ <paramdef><type>boolean</type> <parameter>preserveEndPoints = false</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsection>
+ <title>Description</title>
+ <para> Returns a "smoothed" version of the given geometry using the Chaikin algorithm.
+ See <ulink url="http://www.idav.ucdavis.edu/education/CAGDNotes/Chaikins-Algorithm/Chaikins-Algorithm.html">Chaikins-Algorithm</ulink> for an explanation of the process.
+ For each iteration the number of vertex points will double.
+ The function puts new vertex points at 1/4 of the line before and after each point and removes the original point.
+ To reduce the number of points use one of the simplification functions on the result.
+ The new points gets interpolated values for all included dimensions, also z and m.</para>
+ <para>Second argument, number of iterations is limited to max 5 iterations</para>
+ <para>Note third argument is only valid for polygons, and will be ignored for linestrings</para>
+ <para>This function handles 3D and the third dimension will affect the result.</para>
+ <note><para>Note that returned geometry will get more points than the original.
+ To reduce the number of points again use one of the simplification functions on the result.
+ (see <xref linkend="ST_Simplify" /> and <xref linkend="ST_SimplifyVW" />)</para></note>
+ <para>Availability: 2.5.0</para>
+ </refsection>
+
+ <refsection>
+ <title>Examples</title>
+ <para>A triangle is smoothed</para>
+ <programlisting>
+select ST_AsText(ST_ChaikinSmoothing(geom)) smoothed
+FROM (SELECT 'POLYGON((0 0, 8 8, 0 16, 0 0))'::geometry geom) As foo;
+┌───────────────────────────────────────────┐
+│ smoothed │
+├───────────────────────────────────────────┤
+│ POLYGON((2 2,6 6,6 10,2 14,0 12,0 4,2 2)) │
+└───────────────────────────────────────────┘
+ </programlisting>
+ </refsection>
+ <refsection>
+ <title>See Also</title>
+ <para><xref linkend="ST_Simplify" />, <xref linkend="ST_SimplifyVW" /></para>
+ </refsection>
+ </refentry>
+
+
<refentry id="ST_ConcaveHull">
<refnamediv>
<refname>ST_ConcaveHull</refname>
@@ -2303,6 +2357,104 @@ FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As geom) As foo;
</refsection>
</refentry>
+
+ <refentry id="ST_SimplifyPolygonHull">
+ <refnamediv>
+ <refname>ST_SimplifyPolygonHull</refname>
+ <refpurpose>Computes a boundary-respecting fully exterior or fully interior hull of a polygonal geometry.</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>geometry <function>ST_SimplifyPolygonHull</function></funcdef>
+ <paramdef><type>geometry </type> <parameter>param_geom</parameter></paramdef>
+ <paramdef><type>float </type> <parameter>vertex_fraction</parameter></paramdef>
+ <paramdef choice="opt"><type>boolean </type> <parameter>is_outer = true</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsection>
+ <title>Description</title>
+
+ <para>Computes a boundary-respecting simplified hull of a polygonal geometry.
+ An "outer" hull completely covers the input geometry. An "inner" hull is completely contained by the input geometry.
+ The result is a polygonal geometry formed by a subset of the input vertices.
+ MultiPolygons and holes are handled and produce a result with the same structure as the input.
+ </para>
+
+ <para>The reduction in vertex count is controlled by the <varname>vertex_fraction</varname> parameter,
+ which is a number in the range 0 to 1.
+ Lower values produce simpler results, with smaller vertex count and less concaveness.
+ For both outer and inner hulls a vertex fraction of 1.0 produces the orginal geometry.
+ For outer hulls a value of 0.0 produces the convex hull (for a single polygon);
+ for inner hulls it produces a triangle.</para>
+
+ <para>
+ The simplification process operates by progressively removing concave corners that contain the least amount of area, until the vertex count target is reached.
+ It prevents result edges from crossing, so the result is always a valid polygonal geometry.
+ </para>
+
+ <para>To get better results with geometries that contain relatively long line segments, it might be necessary to "segmentize" the input, as shown below.</para>
+ </refsection>
+ <refsection>
+ <title>Examples</title>
+
+ <para>
+ <informalfigure>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="images/st_simplifypolygonhull02.png" />
+ </imageobject>
+ <caption><para>Outer hull of a Polygon</para></caption>
+ </mediaobject>
+ </informalfigure>
+ <programlisting>SELECT ST_SimplifyPolygonHull(
+ 'POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))',
+ 0.3);
+</programlisting>
+ </para>
+
+ <para>
+ <informalfigure>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="images/st_simplifypolygonhull03.png" />
+ </imageobject>
+ <caption><para>Inner hull of a Polygon</para></caption>
+ </mediaobject>
+ </informalfigure>
+ <programlisting>SELECT ST_SimplifyPolygonHull(
+ 'POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))',
+ 0.3, false);
+</programlisting>
+ </para>
+
+ <para>
+ <informalfigure>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="images/st_simplifypolygonhull01.png" />
+ </imageobject>
+ <caption><para>Outer hull simplification of a MultiPolygon, with segmentization</para></caption>
+ </mediaobject>
+ </informalfigure>
+ <programlisting>SELECT ST_SimplifyPolygonHull(
+ ST_Segmentize(ST_Letters('xt'), 2.0),
+ 0.1);
+</programlisting>
+ </para>
+
+ </refsection>
+
+ <refsection>
+ <title>See Also</title>
+ <para><xref linkend="ST_ConvexHull" />, <xref linkend="ST_SimplifyVW" />, <xref linkend="ST_ConcaveHull" />, <xref linkend="ST_Segmentize" /></para>
+ </refsection>
+ </refentry>
+
+
<refentry id="ST_SimplifyVW">
<refnamediv>
<refname>ST_SimplifyVW</refname>
@@ -2352,111 +2504,6 @@ LINESTRING(5 2,7 25,10 10)
</refsection>
</refentry>
- <refentry id="ST_ChaikinSmoothing">
- <refnamediv>
- <refname>ST_ChaikinSmoothing</refname>
- <refpurpose>Returns a smoothed version of a geometry, using the Chaikin algorithm</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>geometry <function>ST_ChaikinSmoothing</function></funcdef>
- <paramdef><type>geometry</type> <parameter>geom</parameter></paramdef>
- <paramdef><type>integer</type> <parameter>nIterations = 1</parameter></paramdef>
- <paramdef><type>boolean</type> <parameter>preserveEndPoints = false</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsection>
- <title>Description</title>
- <para> Returns a "smoothed" version of the given geometry using the Chaikin algorithm.
- See <ulink url="http://www.idav.ucdavis.edu/education/CAGDNotes/Chaikins-Algorithm/Chaikins-Algorithm.html">Chaikins-Algorithm</ulink> for an explanation of the process.
- For each iteration the number of vertex points will double.
- The function puts new vertex points at 1/4 of the line before and after each point and removes the original point.
- To reduce the number of points use one of the simplification functions on the result.
- The new points gets interpolated values for all included dimensions, also z and m.</para>
- <para>Second argument, number of iterations is limited to max 5 iterations</para>
- <para>Note third argument is only valid for polygons, and will be ignored for linestrings</para>
- <para>This function handles 3D and the third dimension will affect the result.</para>
- <note><para>Note that returned geometry will get more points than the original.
- To reduce the number of points again use one of the simplification functions on the result.
- (see <xref linkend="ST_Simplify" /> and <xref linkend="ST_SimplifyVW" />)</para></note>
- <para>Availability: 2.5.0</para>
- </refsection>
-
- <refsection>
- <title>Examples</title>
- <para>A triangle is smoothed</para>
- <programlisting>
-select ST_AsText(ST_ChaikinSmoothing(geom)) smoothed
-FROM (SELECT 'POLYGON((0 0, 8 8, 0 16, 0 0))'::geometry geom) As foo;
-┌───────────────────────────────────────────┐
-│ smoothed │
-├───────────────────────────────────────────┤
-│ POLYGON((2 2,6 6,6 10,2 14,0 12,0 4,2 2)) │
-└───────────────────────────────────────────┘
- </programlisting>
- </refsection>
- <refsection>
- <title>See Also</title>
- <para><xref linkend="ST_Simplify" />, <xref linkend="ST_SimplifyVW" /></para>
- </refsection>
- </refentry>
-
-
- <refentry id="ST_SimplifyPolygonHull">
- <refnamediv>
- <refname>ST_SimplifyPolygonHull</refname>
- <refpurpose>Computes a boundary-respecting fully exterior or fully interior hull of a polygonal geometry.</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>geometry <function>ST_SimplifyPolygonHull</function></funcdef>
- <paramdef><type>geometry </type> <parameter>param_geom</parameter></paramdef>
- <paramdef><type>float </type> <parameter>vertex_fraction</parameter></paramdef>
- <paramdef choice="opt"><type>boolean </type> <parameter>is_outer = true</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsection>
- <title>Description</title>
-
- <para>Computes a boundary-respecting hull of a polygonal geometry. An "outer" hull completely covers the input geometry. An "inner" hull is completely contained by the input geometry. The degree of reduction in vertices is controlled by the <varname>vertex_fraction</varname> parameter. Larger values produce less concave results. A vertex fraction of 1.0 produces a convex hull; a value of 0.0 produces the original geometry.</para>
-
- <para>The simplification operates by removing the line segments that generate the least amount of extra area, progressively, until the vertex target is reached. To get "nice" results with geometries that have long lines without vertices, it might be necessary to first "pre-segmentize" before running the process, as shown below.</para>
- </refsection>
- <refsection>
- <title>Examples</title>
-
- <para>
- <informalfigure>
- <mediaobject>
- <imageobject>
- <imagedata fileref="images/st_simplifypolygonhull01.png" />
- </imageobject>
- <caption><para>Polygonal simplification of a MultiPolygon</para></caption>
- </mediaobject>
- </informalfigure>
- <programlisting>SELECT ST_SimplifyPolygonHull(
- ST_Segmentize(ST_Letters('xt'), 2.0),
- 0.1);
- </programlisting>
- </para>
-
- </refsection>
-
- <refsection>
- <title>See Also</title>
- <para><xref linkend="ST_ConvexHull" />, <xref linkend="ST_SimplifyVW" />, <xref linkend="ST_ConcaveHull" /></para>
- </refsection>
- </refentry>
-
-
<refentry id="ST_SetEffectiveArea">
<refnamediv>
<refname>ST_SetEffectiveArea</refname>
@@ -2525,6 +2572,7 @@ LINESTRING M (5 2 3.40282346638529e+38,3 8 29,6 20 1.5,7 25 49.5,10 10 3.4028234
</refsection>
</refentry>
+
<refentry id="ST_VoronoiLines">
<refnamediv>
<refname>ST_VoronoiLines</refname>
-----------------------------------------------------------------------
Summary of changes:
doc/html/image_src/Makefile.in | 2 +
doc/html/image_src/st_simplifypolygonhull02.wkt | 2 +
doc/html/image_src/st_simplifypolygonhull03.wkt | 2 +
doc/reference_processing.xml | 258 ++++++++++++++----------
4 files changed, 159 insertions(+), 105 deletions(-)
create mode 100644 doc/html/image_src/st_simplifypolygonhull02.wkt
create mode 100644 doc/html/image_src/st_simplifypolygonhull03.wkt
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