Add optimised method to QgsMapToPixelSimplifier which avoids clones

in unwanted circumstances and works on QgsAbstractGeometry objects instead of QgsGeometry
qgis · Jan 19, 2021 · ff730b6 · ff730b6
1 parent 24d4d4a
commit ff730b6
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Showing 7 changed files with 125 additions and 4 deletions.
diff --git a/python/core/auto_generated/qgsgeometrysimplifier.sip.in b/python/core/auto_generated/qgsgeometrysimplifier.sip.in
@@ -25,6 +25,17 @@ Abstract base class for simplify geometries using a specific algorithm
     virtual QgsGeometry simplify( const QgsGeometry &geometry ) const = 0;
 %Docstring
 Returns a simplified version the specified geometry
+%End
+
+    virtual QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const = 0 /Factory/;
+%Docstring
+Returns a simplified version the specified ``geometry``.
+
+Will return ``None`` if no simplification is to be performed to the geometry.
+
+Caller takes ownership of the returned geometry.
+
+.. versionadded:: 3.18
 %End
 
   public:
@@ -61,6 +72,8 @@ is specified in layer units.
 
     virtual QgsGeometry simplify( const QgsGeometry &geometry ) const;
 
+    virtual QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const /Factory/;
+
 
   protected:
 

diff --git a/python/core/auto_generated/qgsmaptopixelgeometrysimplifier.sip.in b/python/core/auto_generated/qgsmaptopixelgeometrysimplifier.sip.in
@@ -78,9 +78,8 @@ Sets the local simplification algorithm of the vector layer managed
 
     virtual QgsGeometry simplify( const QgsGeometry &geometry ) const;
 
-%Docstring
-Returns a simplified version the specified geometry
-%End
+    virtual QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const /Factory/;
+
 
     void setTolerance( double value );
 %Docstring

diff --git a/src/core/qgsgeometrysimplifier.cpp b/src/core/qgsgeometrysimplifier.cpp
@@ -18,6 +18,7 @@
 #include "qgsgeometrysimplifier.h"
 #include "qgsrectangle.h"
 #include "qgsgeometry.h"
+#include "qgsgeos.h"
 
 bool QgsAbstractGeometrySimplifier::isGeneralizableByDeviceBoundingBox( const QgsRectangle &envelope, float mapToPixelTol )
 {
@@ -47,3 +48,15 @@ QgsGeometry QgsTopologyPreservingSimplifier::simplify( const QgsGeometry &geomet
   return geometry.simplify( mTolerance );
 }
 
+QgsAbstractGeometry *QgsTopologyPreservingSimplifier::simplify( const QgsAbstractGeometry *geometry ) const
+{
+  if ( !geometry )
+  {
+    return nullptr;
+  }
+
+  QgsGeos geos( geometry );
+  std::unique_ptr< QgsAbstractGeometry > simplifiedGeom( geos.simplify( mTolerance ) );
+  return simplifiedGeom.release();
+}
+
diff --git a/src/core/qgsgeometrysimplifier.h b/src/core/qgsgeometrysimplifier.h
@@ -22,8 +22,10 @@
 
 class QgsGeometry;
 class QgsRectangle;
+class QgsAbstractGeometry;
 
 #include "qgis_core.h"
+#include "qgis_sip.h"
 
 /**
  * \ingroup core
@@ -37,6 +39,17 @@ class CORE_EXPORT QgsAbstractGeometrySimplifier
     //! Returns a simplified version the specified geometry
     virtual QgsGeometry simplify( const QgsGeometry &geometry ) const = 0;
 
+    /**
+     * Returns a simplified version the specified \a geometry.
+     *
+     * Will return NULLPTR if no simplification is to be performed to the geometry.
+     *
+     * Caller takes ownership of the returned geometry.
+     *
+     * \since QGIS 3.18
+     */
+    virtual QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const = 0 SIP_FACTORY;
+
     // MapToPixel simplification helper methods
   public:
     //! Returns whether the device-envelope can be replaced by its BBOX when is applied the specified tolerance
@@ -65,6 +78,7 @@ class CORE_EXPORT QgsTopologyPreservingSimplifier : public QgsAbstractGeometrySi
     QgsTopologyPreservingSimplifier( double tolerance );
 
     QgsGeometry simplify( const QgsGeometry &geometry ) const override;
+    QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const override SIP_FACTORY;
 
   protected:
     //! Distance tolerance for the simplification

diff --git a/src/core/qgsmaptopixelgeometrysimplifier.cpp b/src/core/qgsmaptopixelgeometrysimplifier.cpp
@@ -415,3 +415,47 @@ QgsGeometry QgsMapToPixelSimplifier::simplify( const QgsGeometry &geometry ) con
 
   return QgsGeometry( simplifyGeometry( mSimplifyFlags, mSimplifyAlgorithm, *geometry.constGet(), mTolerance, false ) );
 }
+
+QgsAbstractGeometry *QgsMapToPixelSimplifier::simplify( const QgsAbstractGeometry *geometry ) const
+{
+  //
+  // IMPORTANT!!!!!!!
+  // We want to avoid any geometry cloning we possibly can here, which is why the
+  // "fail" paths always return nullptr
+  //
+
+  if ( !geometry )
+  {
+    return nullptr;
+  }
+  if ( mSimplifyFlags == QgsMapToPixelSimplifier::NoFlags )
+  {
+    return nullptr;
+  }
+
+  // Check whether the geometry can be simplified using the map2pixel context
+  const QgsWkbTypes::Type singleType = QgsWkbTypes::singleType( geometry->wkbType() );
+  const QgsWkbTypes::Type flatType = QgsWkbTypes::flatType( singleType );
+  if ( flatType == QgsWkbTypes::Point )
+  {
+    return nullptr;
+  }
+
+  const bool isaLinearRing = flatType == QgsWkbTypes::Polygon;
+  const int numPoints = geometry->nCoordinates();
+
+  if ( numPoints <= ( isaLinearRing ? 6 : 3 ) )
+  {
+    // No simplify simple geometries
+    return nullptr;
+  }
+
+  const QgsRectangle envelope = geometry->boundingBox();
+  if ( std::max( envelope.width(), envelope.height() ) / numPoints > mTolerance * 2.0 )
+  {
+    //points are in average too far apart to lead to any significant simplification
+    return nullptr;
+  }
+
+  return simplifyGeometry( mSimplifyFlags, mSimplifyAlgorithm, *geometry, mTolerance, false ).release();
+}
diff --git a/src/core/qgsmaptopixelgeometrysimplifier.h b/src/core/qgsmaptopixelgeometrysimplifier.h
@@ -89,8 +89,8 @@ class CORE_EXPORT QgsMapToPixelSimplifier : public QgsAbstractGeometrySimplifier
     //! Sets the local simplification algorithm of the vector layer managed
     void setSimplifyAlgorithm( SimplifyAlgorithm simplifyAlgorithm ) { mSimplifyAlgorithm = simplifyAlgorithm; }
 
-    //! Returns a simplified version the specified geometry
     QgsGeometry simplify( const QgsGeometry &geometry ) const override;
+    QgsAbstractGeometry *simplify( const QgsAbstractGeometry *geometry ) const override SIP_FACTORY;
 
     //! Sets the tolerance of the vector layer managed
     void setTolerance( double value ) { mTolerance = value; }

diff --git a/tests/src/core/testqgsmaptopixelgeometrysimplifier.cpp b/tests/src/core/testqgsmaptopixelgeometrysimplifier.cpp
@@ -77,6 +77,7 @@ class TestQgsMapToPixelGeometrySimplifier : public QObject
     void testCircularString();
     void testVisvalingam();
     void testRingValidity();
+    void testAbstractGeometrySimplify();
 
 };
 
@@ -217,5 +218,42 @@ void TestQgsMapToPixelGeometrySimplifier::testRingValidity()
 
 }
 
+void TestQgsMapToPixelGeometrySimplifier::testAbstractGeometrySimplify()
+{
+  // test direct simplification of abstract geometries, especially the "no simplification required" paths
+  QgsMapToPixelSimplifier simplifier( QgsMapToPixelSimplifier::SimplifyGeometry, 5 );
+  std::unique_ptr< QgsAbstractGeometry > simplified;
+
+  // no input geometry
+  simplified.reset( simplifier.simplify( nullptr ) );
+  QVERIFY( !simplified.get() );
+
+  // no simplification flag
+  simplifier.setSimplifyFlags( QgsMapToPixelSimplifier::NoFlags );
+  simplified.reset( simplifier.simplify( nullptr ) );
+  QVERIFY( !simplified.get() );
+
+  simplifier.setSimplifyFlags( QgsMapToPixelSimplifier::SimplifyGeometry );
+  // point geometry = no simplification
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "Point( 1 2 )" ) ).constGet() ) );
+  QVERIFY( !simplified.get() );
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "PointZ( 1 2 3 )" ) ).constGet() ) );
+  QVERIFY( !simplified.get() );
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "MultiPoint( 1 2, 3 4 )" ) ).constGet() ) );
+  QVERIFY( !simplified.get() );
+
+  // triangle polygon = no simplification
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "Polygon(( 1 1, 1 2, 2 2, 1 1))" ) ).constGet() ) );
+  QVERIFY( !simplified.get() );
+
+  // too large bounding box vs tolerance
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "LineString( 1 1, 50 1.5, 100 2, 100 200 )" ) ).constGet() ) );
+  QVERIFY( !simplified.get() );
+
+  // should be simplified
+  simplified.reset( simplifier.simplify( QgsGeometry::fromWkt( QStringLiteral( "LineString( 1 1, 2 1.1, 2.1 1.09, 3 0.9, 4 1 )" ) ).constGet() ) );
+  QCOMPARE( simplified->asWkt( 2 ), QStringLiteral( "LineString (1 1, 2 1.1, 3 0.9, 4 1)" ) );
+}
+
 QGSTEST_MAIN( TestQgsMapToPixelGeometrySimplifier )
 #include "testqgsmaptopixelgeometrysimplifier.moc"