[FEATURE][processing] Add "segmentize" algorithms

Adds two new algorithms which expose QgsGeometry's methods for segmentizing curved geometries. "Segmentize by maximum distance": The segmentization is performed by specifying the maximum allowed offset distance between the original curve and the segmentized representation. "Segmentize by maximum angle": The segmentization is performed by specifying the maximum allowed radius angle between vertices on the straightened geometry (e.g the angle of the arc created from the original arc center to consective output vertices on the linearized geometry).
qgis · Mar 4, 2018 · 4232b93 · 4232b93
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diff --git a/python/plugins/processing/tests/testdata/custom/circular_strings.gpkg b/python/plugins/processing/tests/testdata/custom/circular_strings.gpkg
diff --git a/python/plugins/processing/tests/testdata/expected/segmentize_by_angle.gml b/python/plugins/processing/tests/testdata/expected/segmentize_by_angle.gml
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ogr:FeatureCollection
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation="http://ogr.maptools.org/ segmentize_by_angle.xsd"
+     xmlns:ogr="http://ogr.maptools.org/"
+     xmlns:gml="http://www.opengis.net/gml">
+  <gml:boundedBy>
+    <gml:Box>
+      <gml:coord><gml:X>-0.9875563570784498</gml:X><gml:Y>-3.019161406672679</gml:Y></gml:coord>
+      <gml:coord><gml:X>9.807504202322207</gml:X><gml:Y>4.303079673657821</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:segmentize_by_angle fid="1">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>-0.98755635707845,-0.974075743913436 -0.696095751086827,0.344850591369106 -0.005888714481605,1.50594068665349 1.01349196457716,2.39215679681429 2.25929283346249,2.91416844211677 3.60593731102726,3.0193569100738 4.91768379222303,2.6971192154796 6.06230838593327,1.97993688007214</gml:coordinates></gml:LineString></ogr:geometryProperty>
+      <ogr:id>1</ogr:id>
+    </ogr:segmentize_by_angle>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:segmentize_by_angle fid="2">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>6.91442741208296,-3.01916140667268 6.32475035835957,-2.4284524156428 5.95800750896124,-1.67868190262791 5.8536814658075,-0.850568253126039 6.0230037052269,-0.033264075350454 6.44774542579607,0.68524174270488 7.08218001471432,1.22759669304234 7.85800585857777,1.53541222183353 8.69169952127193,1.57554969254374 9.49350766456267,1.34368800721371 9.74057664392659,1.88754171095694 9.80750420232221,2.48112458938787 9.68773977279365,3.06633943289311 9.39300535646221,3.58590805730082 8.95214822603083,3.98897743369522 8.40831748509891,4.23609695307115 7.81474082890195,4.30307967365782 7.22951485804922,4.18336962947338 6.70991884580703,3.88868349864743</gml:coordinates></gml:LineString></ogr:geometryProperty>
+      <ogr:id>2</ogr:id>
+    </ogr:segmentize_by_angle>
+  </gml:featureMember>
+</ogr:FeatureCollection>
diff --git a/python/plugins/processing/tests/testdata/expected/segmentize_by_angle.xsd b/python/plugins/processing/tests/testdata/expected/segmentize_by_angle.xsd
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xs:schema targetNamespace="http://ogr.maptools.org/" xmlns:ogr="http://ogr.maptools.org/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:gml="http://www.opengis.net/gml" elementFormDefault="qualified" version="1.0">
+<xs:import namespace="http://www.opengis.net/gml" schemaLocation="http://schemas.opengis.net/gml/2.1.2/feature.xsd"/>
+<xs:element name="FeatureCollection" type="ogr:FeatureCollectionType" substitutionGroup="gml:_FeatureCollection"/>
+<xs:complexType name="FeatureCollectionType">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureCollectionType">
+      <xs:attribute name="lockId" type="xs:string" use="optional"/>
+      <xs:attribute name="scope" type="xs:string" use="optional"/>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+<xs:element name="segmentize_by_angle" type="ogr:segmentize_by_angle_Type" substitutionGroup="gml:_Feature"/>
+<xs:complexType name="segmentize_by_angle_Type">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence>
+        <xs:element name="geometryProperty" type="gml:LineStringPropertyType" nillable="true" minOccurs="0" maxOccurs="1"/>
+        <xs:element name="id" nillable="true" minOccurs="0" maxOccurs="1">
+          <xs:simpleType>
+            <xs:restriction base="xs:integer">
+              <xs:totalDigits value="10"/>
+            </xs:restriction>
+          </xs:simpleType>
+        </xs:element>
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+</xs:schema>
diff --git a/python/plugins/processing/tests/testdata/expected/segmentize_by_distance.gml b/python/plugins/processing/tests/testdata/expected/segmentize_by_distance.gml
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ogr:FeatureCollection
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation="http://ogr.maptools.org/ segmentize_by_distance.xsd"
+     xmlns:ogr="http://ogr.maptools.org/"
+     xmlns:gml="http://www.opengis.net/gml">
+  <gml:boundedBy>
+    <gml:Box>
+      <gml:coord><gml:X>-0.9875563570784498</gml:X><gml:Y>-3.019161406672679</gml:Y></gml:coord>
+      <gml:coord><gml:X>9.794917283570138</gml:X><gml:Y>4.303894025825194</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:segmentize_by_distance fid="1">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>-0.98755635707845,-0.974075743913436 -0.212652411335007,1.23725667259743 1.61554353037206,2.70291924637298 3.94247675733233,2.9783261066885 6.06230838593327,1.97993688007214</gml:coordinates></gml:LineString></ogr:geometryProperty>
+      <ogr:id>1</ogr:id>
+    </ogr:segmentize_by_distance>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:segmentize_by_distance fid="2">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>6.91442741208296,-3.01916140667268 5.90638239076692,-1.47558750786245 6.20570477434748,0.34352800709968 7.65518199185988,1.48273428429481 9.49350766456267,1.34368800721371 9.79491728357014,2.63050854973142 9.18843697294715,3.80478981923308 7.96465191909257,4.30389402582519 6.70991884580703,3.88868349864743</gml:coordinates></gml:LineString></ogr:geometryProperty>
+      <ogr:id>2</ogr:id>
+    </ogr:segmentize_by_distance>
+  </gml:featureMember>
+</ogr:FeatureCollection>
diff --git a/python/plugins/processing/tests/testdata/expected/segmentize_by_distance.xsd b/python/plugins/processing/tests/testdata/expected/segmentize_by_distance.xsd
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xs:schema targetNamespace="http://ogr.maptools.org/" xmlns:ogr="http://ogr.maptools.org/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:gml="http://www.opengis.net/gml" elementFormDefault="qualified" version="1.0">
+<xs:import namespace="http://www.opengis.net/gml" schemaLocation="http://schemas.opengis.net/gml/2.1.2/feature.xsd"/>
+<xs:element name="FeatureCollection" type="ogr:FeatureCollectionType" substitutionGroup="gml:_FeatureCollection"/>
+<xs:complexType name="FeatureCollectionType">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureCollectionType">
+      <xs:attribute name="lockId" type="xs:string" use="optional"/>
+      <xs:attribute name="scope" type="xs:string" use="optional"/>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+<xs:element name="segmentize_by_distance" type="ogr:segmentize_by_distance_Type" substitutionGroup="gml:_Feature"/>
+<xs:complexType name="segmentize_by_distance_Type">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence>
+        <xs:element name="geometryProperty" type="gml:LineStringPropertyType" nillable="true" minOccurs="0" maxOccurs="1"/>
+        <xs:element name="id" nillable="true" minOccurs="0" maxOccurs="1">
+          <xs:simpleType>
+            <xs:restriction base="xs:integer">
+              <xs:totalDigits value="10"/>
+            </xs:restriction>
+          </xs:simpleType>
+        </xs:element>
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+</xs:schema>
diff --git a/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml b/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml
@@ -4794,3 +4794,27 @@ tests:
       OUTPUT:
         name: expected/multiring_buffer.gml
         type: vector
+
+  - algorithm: native:segmentizebymaxangle
+    name: Segmentize by angle
+    params:
+      ANGLE: 20.0
+      INPUT:
+        name: custom/circular_strings.gpkg|layername=circular_strings
+        type: vector
+    results:
+      OUTPUT:
+        name: expected/segmentize_by_angle.gml
+        type: vector
+
+  - algorithm: native:segmentizebymaxdistance
+    name: Segmentize by distance
+    params:
+      DISTANCE: 0.2
+      INPUT:
+        name: custom/circular_strings.gpkg|layername=circular_strings
+        type: vector
+    results:
+      OUTPUT:
+        name: expected/segmentize_by_distance.gml
+        type: vector
diff --git a/src/analysis/CMakeLists.txt b/src/analysis/CMakeLists.txt
@@ -59,6 +59,7 @@ SET(QGIS_ANALYSIS_SRCS
   processing/qgsalgorithmremovenullgeometry.cpp
   processing/qgsalgorithmrenamelayer.cpp
   processing/qgsalgorithmsaveselectedfeatures.cpp
+  processing/qgsalgorithmsegmentize.cpp
   processing/qgsalgorithmsimplify.cpp
   processing/qgsalgorithmsmooth.cpp
   processing/qgsalgorithmsnaptogrid.cpp

diff --git a/src/analysis/processing/qgsalgorithmsegmentize.cpp b/src/analysis/processing/qgsalgorithmsegmentize.cpp
@@ -0,0 +1,197 @@
+/***************************************************************************
+                         qgsalgorithmsegmentize.cpp
+                         ---------------------
+    begin                : March 2018
+    copyright            : (C) 2018 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsalgorithmsegmentize.h"
+
+///@cond PRIVATE
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::name() const
+{
+  return QStringLiteral( "segmentizebymaxdistance" );
+}
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::displayName() const
+{
+  return QObject::tr( "Segmentize by maximum distance" );
+}
+
+QStringList QgsSegmentizeByMaximumDistanceAlgorithm::tags() const
+{
+  return QObject::tr( "straighten,linearize,densify,curves,curved,circular" ).split( ',' );
+}
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::group() const
+{
+  return QObject::tr( "Vector geometry" );
+}
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::groupId() const
+{
+  return QStringLiteral( "vectorgeometry" );
+}
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::outputName() const
+{
+  return QObject::tr( "Segmentized" );
+}
+
+QString QgsSegmentizeByMaximumDistanceAlgorithm::shortHelpString() const
+{
+  return QObject::tr( "This algorithm segmentizes a geometry by converting curved sections to linear sections.\n\n"
+                      "The segmentization is performed by specifying the maximum allowed offset distance between the original"
+                      "curve and the segmentized representation.\n\n"
+                      "Non-curved geometries will be retained without change." );
+}
+
+QgsSegmentizeByMaximumDistanceAlgorithm *QgsSegmentizeByMaximumDistanceAlgorithm::createInstance() const
+{
+  return new QgsSegmentizeByMaximumDistanceAlgorithm();
+}
+
+QList<int> QgsSegmentizeByMaximumDistanceAlgorithm::inputLayerTypes() const
+{
+  return QList<int>() << QgsProcessing::TypeVectorLine << QgsProcessing::TypeVectorPolygon;
+}
+
+void QgsSegmentizeByMaximumDistanceAlgorithm::initParameters( const QVariantMap & )
+{
+  std::unique_ptr< QgsProcessingParameterNumber > tolerance = qgis::make_unique< QgsProcessingParameterNumber >( QStringLiteral( "DISTANCE" ),
+      QObject::tr( "Maximum offset distance" ), QgsProcessingParameterNumber::Double,
+      1.0, false, 0, 10000000.0 );
+  tolerance->setIsDynamic( true );
+  tolerance->setDynamicPropertyDefinition( QgsPropertyDefinition( QStringLiteral( "DISTANCE" ), QObject::tr( "Maximum offset distance" ), QgsPropertyDefinition::DoublePositive ) );
+  tolerance->setDynamicLayerParameterName( QStringLiteral( "INPUT" ) );
+  addParameter( tolerance.release() );
+}
+
+bool QgsSegmentizeByMaximumDistanceAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
+{
+  mTolerance = parameterAsDouble( parameters, QStringLiteral( "DISTANCE" ), context );
+  mDynamicTolerance = QgsProcessingParameters::isDynamic( parameters, QStringLiteral( "DISTANCE" ) );
+  if ( mDynamicTolerance )
+    mToleranceProperty = parameters.value( QStringLiteral( "DISTANCE" ) ).value< QgsProperty >();
+
+  return true;
+}
+
+QgsFeatureList QgsSegmentizeByMaximumDistanceAlgorithm::processFeature( const QgsFeature &feature, QgsProcessingContext &context, QgsProcessingFeedback * )
+{
+  QgsFeature f = feature;
+  if ( f.hasGeometry() )
+  {
+    QgsGeometry geometry = f.geometry();
+    double tolerance = mTolerance;
+    if ( mDynamicTolerance )
+      tolerance = mToleranceProperty.valueAsDouble( context.expressionContext(), tolerance );
+    geometry.convertToStraightSegment( tolerance, QgsAbstractGeometry::MaximumDifference );
+    f.setGeometry( geometry );
+  }
+  return QgsFeatureList() << f;
+}
+
+
+
+
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::name() const
+{
+  return QStringLiteral( "segmentizebymaxangle" );
+}
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::displayName() const
+{
+  return QObject::tr( "Segmentize by maximum angle" );
+}
+
+QStringList QgsSegmentizeByMaximumAngleAlgorithm::tags() const
+{
+  return QObject::tr( "straighten,linearize,densify,curves,curved,circular,angle" ).split( ',' );
+}
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::group() const
+{
+  return QObject::tr( "Vector geometry" );
+}
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::groupId() const
+{
+  return QStringLiteral( "vectorgeometry" );
+}
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::outputName() const
+{
+  return QObject::tr( "Segmentized" );
+}
+
+QString QgsSegmentizeByMaximumAngleAlgorithm::shortHelpString() const
+{
+  return QObject::tr( "This algorithm segmentizes a geometry by converting curved sections to linear sections.\n\n"
+                      "The segmentization is performed by specifying the maximum allowed radius angle between vertices"
+                      "on the straightened geometry (e.g the angle of the arc created from the original arc center to consective"
+                      "output vertices on the linearized geometry).\n\n"
+                      "Non-curved geometries will be retained without change." );
+}
+
+QgsSegmentizeByMaximumAngleAlgorithm *QgsSegmentizeByMaximumAngleAlgorithm::createInstance() const
+{
+  return new QgsSegmentizeByMaximumAngleAlgorithm();
+}
+
+QList<int> QgsSegmentizeByMaximumAngleAlgorithm::inputLayerTypes() const
+{
+  return QList<int>() << QgsProcessing::TypeVectorLine << QgsProcessing::TypeVectorPolygon;
+}
+
+void QgsSegmentizeByMaximumAngleAlgorithm::initParameters( const QVariantMap & )
+{
+  std::unique_ptr< QgsProcessingParameterNumber > tolerance = qgis::make_unique< QgsProcessingParameterNumber >( QStringLiteral( "ANGLE" ),
+      QObject::tr( "Maximum angle between vertices (degrees)" ), QgsProcessingParameterNumber::Double,
+      5.0, false, 0, 360.0 );
+  tolerance->setIsDynamic( true );
+  tolerance->setDynamicPropertyDefinition( QgsPropertyDefinition( QStringLiteral( "ANGLE" ), QObject::tr( "Maximum angle between vertices (degrees)" ), QgsPropertyDefinition::DoublePositive ) );
+  tolerance->setDynamicLayerParameterName( QStringLiteral( "INPUT" ) );
+  addParameter( tolerance.release() );
+}
+
+bool QgsSegmentizeByMaximumAngleAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
+{
+  mTolerance = parameterAsDouble( parameters, QStringLiteral( "ANGLE" ), context );
+  mDynamicTolerance = QgsProcessingParameters::isDynamic( parameters, QStringLiteral( "ANGLE" ) );
+  if ( mDynamicTolerance )
+    mToleranceProperty = parameters.value( QStringLiteral( "ANGLE" ) ).value< QgsProperty >();
+
+  return true;
+}
+
+QgsFeatureList QgsSegmentizeByMaximumAngleAlgorithm::processFeature( const QgsFeature &feature, QgsProcessingContext &context, QgsProcessingFeedback * )
+{
+  QgsFeature f = feature;
+  if ( f.hasGeometry() )
+  {
+    QgsGeometry geometry = f.geometry();
+    double tolerance = mTolerance;
+    if ( mDynamicTolerance )
+      tolerance = mToleranceProperty.valueAsDouble( context.expressionContext(), tolerance );
+    geometry.convertToStraightSegment( M_PI * tolerance / 180.0, QgsAbstractGeometry::MaximumAngle );
+    f.setGeometry( geometry );
+  }
+  return QgsFeatureList() << f;
+}
+
+///@endcond
+
+