Add extrude function to QgsGeometry

python/core/geometry/qgsgeometry.sip

@@ -433,9 +433,12 @@ class QgsGeometry
     /** Returns a geometry representing the points making up this geometry that do not make up other. */
     QgsGeometry* difference( const QgsGeometry* geometry ) const /Factory/;
 
-    /** Returns a Geometry representing the points making up this Geometry that do not make up other. */
+    /** Returns a Geometry representing the points making up this geometry that do not make up other. */
     QgsGeometry* symDifference( const QgsGeometry* geometry ) const /Factory/;
 
+    /** Returns an extruded version of this geometry. */
+    QgsGeometry extrude( double x, double y );
+
     /** Exports the geometry to WKT
      *  @note precision parameter added in 2.4
      *  @return true in case of success and false else

resources/function_help/json/extrude

@@ -0,0 +1,20 @@
+{
+  "name": "extrude",
+  "type": "function",
+  "description": "Returns an extruded version of the input (Multi-)Curve or (Multi-)Linestring geometry with an extension specified by x and y.",
+  "arguments": [
+    {"arg":"geom","description":"a polygon geometry"},
+    {"arg":"x","description":"x extension, numeric value"},
+    {"arg":"y","description":"y extension, numeric value"}
+  ],
+  "examples": [
+    {
+      "expression":"extrude(geom_from_wkt('LineString(1 2, 3 2, 4 3)'), 1, 2)",
+      "returns":"Polygon ((1 2, 3 2, 4 3, 5 5, 4 4, 2 4, 1 2))"
+    },
+    {
+      "expression":"extrude(geom_from_wkt('MultiLineString((1 2, 3 2), (4 3, 8 3)'), 1, 2)",
+      "returns":"MultiPolygon (((1 2, 3 2, 4 4, 2 4, 1 2)),((4 3, 8 3, 9 5, 5 5, 4 3)))"
+    }
+  ]
+}

src/core/CMakeLists.txt

@@ -320,6 +320,7 @@ SET(QGIS_CORE_SRCS
   geometry/qgsgeometry.cpp
   geometry/qgsgeometrycollectionv2.cpp
   geometry/qgsgeometryeditutils.cpp
+  geometry/qgsinternalgeometryengine.cpp
   geometry/qgsgeometryfactory.cpp
   geometry/qgsgeometryutils.cpp
   geometry/qgsgeos.cpp
@@ -788,6 +789,7 @@ SET(QGIS_CORE_HDRS
   layertree/qgslayertreeutils.h
 
   geometry/qgsgeometry.h
+  geometry/qgsinternalgeometryengine.h
   geometry/qgsabstractgeometryv2.h
   geometry/qgswkbtypes.h
   geometry/qgspointv2.h

src/core/geometry/qgsgeometry.cpp

@@ -23,6 +23,7 @@ email                : morb at ozemail dot com dot au
 #include "qgsgeometryeditutils.h"
 #include "qgsgeometryfactory.h"
 #include "qgsgeometryutils.h"
+#include "qgsinternalgeometryengine.h"
 #include "qgsgeos.h"
 #include "qgsapplication.h"
 #include "qgslogger.h"
@@ -1404,6 +1405,13 @@ QgsGeometry* QgsGeometry::symDifference( const QgsGeometry* geometry ) const
   return new QgsGeometry( resultGeom );
 }
 
+QgsGeometry QgsGeometry::extrude( double x, double y )
+{
+  QgsInternalGeometryEngine engine( *this );
+
+  return engine.extrude( x, y );
+}
+
 QList<QgsGeometry*> QgsGeometry::asGeometryCollection() const
 {
   QList<QgsGeometry*> geometryList;

src/core/geometry/qgsgeometry.h

@@ -480,9 +480,12 @@ class CORE_EXPORT QgsGeometry
     /** Returns a geometry representing the points making up this geometry that do not make up other. */
     QgsGeometry* difference( const QgsGeometry* geometry ) const;
 
-    /** Returns a Geometry representing the points making up this Geometry that do not make up other. */
+    /** Returns a geometry representing the points making up this geometry that do not make up other. */
     QgsGeometry* symDifference( const QgsGeometry* geometry ) const;
 
+    /** Returns an extruded version of this geometry. */
+    QgsGeometry extrude( double x, double y );
+
     /** Exports the geometry to WKT
      *  @note precision parameter added in 2.4
      *  @return true in case of success and false else

src/core/geometry/qgsgeometryengine.h

@@ -13,8 +13,8 @@ email                : marco.hugentobler at sourcepole dot com
  *                                                                         *
  ***************************************************************************/
 
-#ifndef QGSVECTORTOPOLOGY_H
+#ifndef QGSGEOMETRYENGINE_H
-#define QGSVECTORTOPOLOGY_H
+#define QGSGEOMETRYENGINE_H
 
 #include "qgspointv2.h"
 #include "qgslinestringv2.h"
@@ -106,4 +106,4 @@ class CORE_EXPORT QgsGeometryEngine
     QgsGeometryEngine();
 };
 
-#endif // QGSVECTORTOPOLOGY_H
+#endif // QGSGEOMETRYENGINE_H

src/core/geometry/qgsinternalgeometryengine.cpp

@@ -0,0 +1,88 @@
+/***************************************************************************
+  qgsinternalgeometryengine.cpp - QgsInternalGeometryEngine
+
+ ---------------------
+ begin                : 13.1.2016
+ copyright            : (C) 2016 by Matthias Kuhn
+ email                : matthias@opengis.ch
+ ***************************************************************************
+ *                                                                         *
+ *   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 "qgsinternalgeometryengine.h"
+
+#include "qgslinestringv2.h"
+#include "qgsmultipolygonv2.h"
+#include "qgspolygonv2.h"
+#include "qgsmulticurvev2.h"
+
+#include <QTransform>
+
+QgsInternalGeometryEngine::QgsInternalGeometryEngine( const QgsGeometry& geometry )
+    : mGeometry( geometry.geometry() )
+{
+
+}
+
+/***************************************************************************
+ * This class is considered CRITICAL and any change MUST be accompanied with
+ * full unit tests.
+ * See details in QEP #17
+ ****************************************************************************/
+
+QgsGeometry QgsInternalGeometryEngine::extrude( double x, double y )
+{
+  QList<QgsLineStringV2*> linesToProcess;
+
+  const QgsMultiCurveV2* multiCurve = dynamic_cast< const QgsMultiCurveV2* >( mGeometry );
+  if ( multiCurve )
+  {
+    for ( int i = 0; i < multiCurve->partCount(); ++i )
+    {
+      linesToProcess << static_cast<QgsLineStringV2*>( multiCurve->geometryN( i )->clone() );
+    }
+  }
+
+  const QgsCurveV2* curve = dynamic_cast< const QgsCurveV2* >( mGeometry );
+  if ( curve )
+  {
+    linesToProcess << static_cast<QgsLineStringV2*>( curve->segmentize() );
+  }
+
+  QgsMultiPolygonV2* multipolygon = linesToProcess.size() > 1 ? new QgsMultiPolygonV2() : nullptr;
+  QgsPolygonV2* polygon;
+
+  if ( !linesToProcess.empty() )
+  {
+    Q_FOREACH ( QgsLineStringV2* line, linesToProcess )
+    {
+      QTransform transform = QTransform::fromTranslate( x, y );
+
+      QgsLineStringV2* secondline = line->reversed();
+      secondline->transform( transform );
+
+      line->append( secondline );
+      line->addVertex( line->pointN( 0 ) );
+
+      polygon = new QgsPolygonV2();
+      polygon->setExteriorRing( line );
+
+      if ( multipolygon )
+        multipolygon->addGeometry( polygon );
+
+      delete secondline;
+    }
+
+    if ( multipolygon )
+      return QgsGeometry( multipolygon );
+    else
+      return QgsGeometry( polygon );
+  }
+
+  return QgsGeometry();
+}

src/core/geometry/qgsinternalgeometryengine.h

@@ -0,0 +1,54 @@
+/***************************************************************************
+  qgsinternalgeometryengine.h - QgsInternalGeometryEngine
+
+ ---------------------
+ begin                : 13.1.2016
+ copyright            : (C) 2016 by Matthias Kuhn
+ email                : matthias@opengis.ch
+ ***************************************************************************
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#ifndef QGSINTERNALGEOMETRYENGINE_H
+#define QGSINTERNALGEOMETRYENGINE_H
+
+#include "qgsgeometry.h"
+
+/**
+ * This class offers geometry processing methods.
+ *
+ * The methods are available via QgsGeometry::[geometryfunction]
+ * and therefore this does not need to be accessed directly.
+ *
+ * @note not available in Python bindings
+ */
+
+class QgsInternalGeometryEngine
+{
+  public:
+    /**
+     * The caller is responsible that the geometry is available and unchanged
+     * for the whole lifetime of this object.
+     * @param geometry
+     */
+    QgsInternalGeometryEngine( const QgsGeometry& geometry );
+
+    /**
+     * Will extrude a line or (segmentized) curve by a given offset and return a polygon
+     * representation of it.
+     *
+     * @param x offset in x direction
+     * @param y offset in y direction
+     * @return an extruded polygon
+     */
+    QgsGeometry extrude( double x, double y );
+
+  private:
+    const QgsAbstractGeometryV2* mGeometry;
+};
+
+#endif // QGSINTERNALGEOMETRYENGINE_H

src/core/qgsexpression.cpp

@@ -2153,6 +2153,21 @@ static QVariant fcnAzimuth( const QVariantList& values, const QgsExpressionConte
   return QVariant();
 }
 
+static QVariant fcnExtrude( const QVariantList& values, const QgsExpressionContext*, QgsExpression* parent )
+{
+  if ( values.length() != 3 )
+    return QVariant();
+
+  QgsGeometry fGeom = getGeometry( values.at( 0 ), parent );
+  double x = getDoubleValue( values.at( 1 ), parent );
+  double y = getDoubleValue( values.at( 2 ), parent );
+
+  QgsGeometry geom = fGeom.extrude( x, y );
+
+  QVariant result = geom.geometry() ? QVariant::fromValue( geom ) : QVariant();
+  return result;
+}
+
 static QVariant fcnRound( const QVariantList& values, const QgsExpressionContext *, QgsExpression* parent )
 {
   if ( values.length() == 2 )
@@ -2915,6 +2930,7 @@ const QList<QgsExpression::Function*>& QgsExpression::Functions()
     << new StaticFunction( "geom_to_wkt", -1, fcnGeomToWKT, "GeometryGroup", QString(), false, QStringList(), false, QStringList() << "geomToWKT" )
     << new StaticFunction( "geometry", 1, fcnGetGeometry, "GeometryGroup", QString(), true )
     << new StaticFunction( "transform", 3, fcnTransformGeometry, "GeometryGroup" )
+    << new StaticFunction( "extrude", 3, fcnExtrude, "GeometryGroup", QString() )
     << new StaticFunction( "$rownum", 0, fcnRowNumber, "deprecated" )
     << new StaticFunction( "$id", 0, fcnFeatureId, "Record" )
     << new StaticFunction( "$currentfeature", 0, fcnFeature, "Record" )

src/core/qgsexpression.h

@@ -280,7 +280,7 @@ class CORE_EXPORT QgsExpression
     QgsDistanceArea* geomCalculator();
 
     //! Sets the geometry calculator used in evaluation of expressions,
-    // instead of the default.
+    //! instead of the default.
     void setGeomCalculator( const QgsDistanceArea &calc );
 
     /** This function currently replaces each expression between [% and %]

tests/src/python/test_qgsgeometry.py

@@ -345,7 +345,7 @@ class TestQgsGeometry(TestCase):
                                       'simplify_error.wkt'), 'rt')
         myWKT = myWKTFile.readline()
         myWKTFile.close()
-        print myWKT
+        # print myWKT
         myGeometry = QgsGeometry().fromWkt(myWKT)
         assert myGeometry is not None
         myStartLength = len(myWKT)
@@ -1191,6 +1191,17 @@ class TestQgsGeometry(TestCase):
         expwkt = "MultiPolygon (((0 0, 1 0, 1 1, 2 1, 2 2, 0 2, 0 0)),((4 0, 5 0, 5 2, 3 2, 3 1, 4 1, 4 0)))"
         wkt = polygon.exportToWkt()
 
+    def testExtrude(self):
+        points = [QgsPoint(1, 2), QgsPoint(3, 2), QgsPoint(4, 3)]
+        line = QgsGeometry.fromPolyline(points)
+        expected = QgsGeometry.fromWkt('Polygon ((1 2, 3 2, 4 3, 5 5, 4 4, 2 4, 1 2))')
+        self.assertEqual(line.extrude(1, 2).exportToWkt(), expected.exportToWkt())
+
+        points2 = [[QgsPoint(1, 2), QgsPoint(3, 2)], [QgsPoint(4, 3), QgsPoint(8, 3)]]
+        multiline = QgsGeometry.fromMultiPolyline(points2)
+        expected = QgsGeometry.fromWkt('MultiPolygon (((1 2, 3 2, 4 4, 2 4, 1 2)),((4 3, 8 3, 9 5, 5 5, 4 3)))')
+        self.assertEqual(multiline.extrude(1, 2).exportToWkt(), expected.exportToWkt())
+
     def testBoundingBox(self):
         # 2-+-+-+-+-3
         # |         |