Add option to remove redundant vertices in QgsAbstractGeometry::snapp…

…edToGrid If opted in, then vertices which form a midpoint of a straight line segment will be removed in the output
nyalldawson · Jun 3, 2024 · 57965ee · 57965ee
1 parent ec49513
commit 57965ee
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Showing 28 changed files with 81 additions and 39 deletions.
diff --git a/python/PyQt6/core/auto_generated/geometry/qgsabstractgeometry.sip.in b/python/PyQt6/core/auto_generated/geometry/qgsabstractgeometry.sip.in
@@ -604,7 +604,7 @@ E.g. :py:class:`QgsLineString` -> :py:class:`QgsCompoundCurve`, :py:class:`QgsPo
 :return: the converted geometry. Caller takes ownership
 %End
 
-    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const = 0 /Factory/;
+    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const = 0 /Factory/;
 %Docstring
 Makes a new geometry with all the points or vertices snapped to the closest point of the grid.
 Ownership is transferred to the caller.
@@ -626,6 +626,7 @@ In this case, it can be thought like rounding the x and y of all the points/vert
 :param vSpacing: Vertical spacing of the grid (y axis). 0 to disable.
 :param dSpacing: Depth spacing of the grid (z axis). 0 (default) to disable.
 :param mSpacing: Custom dimension spacing of the grid (m axis). 0 (default) to disable.
+:param removeRedundantPoints: if ``True``, then points which are redundant (e.g. they represent mid points on a straight line segment) will be skipped (since QGIS 3.38)
 %End
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false ) = 0;

diff --git a/python/PyQt6/core/auto_generated/geometry/qgscircularstring.sip.in b/python/PyQt6/core/auto_generated/geometry/qgscircularstring.sip.in
@@ -151,7 +151,7 @@ Appends the contents of another circular ``string`` to the end of this circular
 
     virtual QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const /Factory/;
 
-    virtual QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/PyQt6/core/auto_generated/geometry/qgscompoundcurve.sip.in b/python/PyQt6/core/auto_generated/geometry/qgscompoundcurve.sip.in
@@ -81,7 +81,7 @@ of the curve.
 :param toleranceType: maximum segmentation angle or maximum difference between approximation and curve
 %End
 
-    virtual QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/PyQt6/core/auto_generated/geometry/qgscurvepolygon.sip.in b/python/PyQt6/core/auto_generated/geometry/qgscurvepolygon.sip.in
@@ -68,7 +68,7 @@ Curve polygon geometry type
 
     virtual QgsAbstractGeometry *boundary() const /Factory/;
 
-    virtual QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/PyQt6/core/auto_generated/geometry/qgsgeometrycollection.sip.in b/python/PyQt6/core/auto_generated/geometry/qgsgeometrycollection.sip.in
@@ -95,7 +95,7 @@ Returns a geometry from within the collection.
 
     virtual void clear();
 
-    virtual QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/PyQt6/core/auto_generated/geometry/qgslinestring.sip.in b/python/PyQt6/core/auto_generated/geometry/qgslinestring.sip.in
@@ -594,7 +594,7 @@ segment in the line.
     int indexOf( const QgsPoint &point ) const final;
     virtual bool isValid( QString &error /Out/, Qgis::GeometryValidityFlags flags = Qgis::GeometryValidityFlags() ) const;
 
-    virtual QgsLineString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsLineString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/PyQt6/core/auto_generated/geometry/qgspoint.sip.in b/python/PyQt6/core/auto_generated/geometry/qgspoint.sip.in
@@ -355,7 +355,7 @@ Example
 
     virtual QgsPoint *clone() const /Factory/;
 
-    virtual QgsPoint *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsPoint *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgsabstractgeometry.sip.in b/python/core/auto_generated/geometry/qgsabstractgeometry.sip.in
@@ -604,7 +604,7 @@ E.g. :py:class:`QgsLineString` -> :py:class:`QgsCompoundCurve`, :py:class:`QgsPo
 :return: the converted geometry. Caller takes ownership
 %End
 
-    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const = 0 /Factory/;
+    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const = 0 /Factory/;
 %Docstring
 Makes a new geometry with all the points or vertices snapped to the closest point of the grid.
 Ownership is transferred to the caller.
@@ -626,6 +626,7 @@ In this case, it can be thought like rounding the x and y of all the points/vert
 :param vSpacing: Vertical spacing of the grid (y axis). 0 to disable.
 :param dSpacing: Depth spacing of the grid (z axis). 0 (default) to disable.
 :param mSpacing: Custom dimension spacing of the grid (m axis). 0 (default) to disable.
+:param removeRedundantPoints: if ``True``, then points which are redundant (e.g. they represent mid points on a straight line segment) will be skipped (since QGIS 3.38)
 %End
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false ) = 0;

diff --git a/python/core/auto_generated/geometry/qgscircularstring.sip.in b/python/core/auto_generated/geometry/qgscircularstring.sip.in
@@ -151,7 +151,7 @@ Appends the contents of another circular ``string`` to the end of this circular
 
     virtual QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const /Factory/;
 
-    virtual QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgscompoundcurve.sip.in b/python/core/auto_generated/geometry/qgscompoundcurve.sip.in
@@ -81,7 +81,7 @@ of the curve.
 :param toleranceType: maximum segmentation angle or maximum difference between approximation and curve
 %End
 
-    virtual QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgscurvepolygon.sip.in b/python/core/auto_generated/geometry/qgscurvepolygon.sip.in
@@ -68,7 +68,7 @@ Curve polygon geometry type
 
     virtual QgsAbstractGeometry *boundary() const /Factory/;
 
-    virtual QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgsgeometrycollection.sip.in b/python/core/auto_generated/geometry/qgsgeometrycollection.sip.in
@@ -95,7 +95,7 @@ Returns a geometry from within the collection.
 
     virtual void clear();
 
-    virtual QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgslinestring.sip.in b/python/core/auto_generated/geometry/qgslinestring.sip.in
@@ -594,7 +594,7 @@ segment in the line.
     int indexOf( const QgsPoint &point ) const final;
     virtual bool isValid( QString &error /Out/, Qgis::GeometryValidityFlags flags = Qgis::GeometryValidityFlags() ) const;
 
-    virtual QgsLineString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsLineString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/python/core/auto_generated/geometry/qgspoint.sip.in b/python/core/auto_generated/geometry/qgspoint.sip.in
@@ -355,7 +355,7 @@ Example
 
     virtual QgsPoint *clone() const /Factory/;
 
-    virtual QgsPoint *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+    virtual QgsPoint *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const /Factory/;
 
     virtual bool removeDuplicateNodes( double epsilon = 4 * DBL_EPSILON, bool useZValues = false );
 

diff --git a/src/core/geometry/qgsabstractgeometry.h b/src/core/geometry/qgsabstractgeometry.h
@@ -644,8 +644,9 @@ class CORE_EXPORT QgsAbstractGeometry
      * \param vSpacing Vertical spacing of the grid (y axis). 0 to disable.
      * \param dSpacing Depth spacing of the grid (z axis). 0 (default) to disable.
      * \param mSpacing Custom dimension spacing of the grid (m axis). 0 (default) to disable.
+     * \param removeRedundantPoints if TRUE, then points which are redundant (e.g. they represent mid points on a straight line segment) will be skipped (since QGIS 3.38)
      */
-    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const = 0 SIP_FACTORY;
+    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const = 0 SIP_FACTORY;
 
     /**
      * Removes duplicate nodes from the geometry, wherever removing the nodes does not result in a

diff --git a/src/core/geometry/qgscircularstring.cpp b/src/core/geometry/qgscircularstring.cpp
@@ -624,7 +624,7 @@ QgsLineString *QgsCircularString::curveToLine( double tolerance, SegmentationTol
   return line;
 }
 
-QgsCircularString *QgsCircularString::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
+QgsCircularString *QgsCircularString::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool ) const
 {
   // prepare result
   std::unique_ptr<QgsCircularString> result { createEmptyWithSameType() };

diff --git a/src/core/geometry/qgscircularstring.h b/src/core/geometry/qgscircularstring.h
@@ -259,7 +259,7 @@ class CORE_EXPORT QgsCircularString: public QgsCurve
     QgsPoint startPoint() const override SIP_HOLDGIL;
     QgsPoint endPoint() const override SIP_HOLDGIL;
     QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const override SIP_FACTORY;
-    QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const override SIP_FACTORY;
+    QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const override SIP_FACTORY;
     bool removeDuplicateNodes( double epsilon = 4 * std::numeric_limits<double>::epsilon(), bool useZValues = false ) override;
 
     void draw( QPainter &p ) const override;

diff --git a/src/core/geometry/qgscompoundcurve.cpp b/src/core/geometry/qgscompoundcurve.cpp
@@ -465,13 +465,13 @@ QgsLineString *QgsCompoundCurve::curveToLine( double tolerance, SegmentationTole
   return line;
 }
 
-QgsCompoundCurve *QgsCompoundCurve::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
+QgsCompoundCurve *QgsCompoundCurve::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool removeRedundantPoints ) const
 {
   std::unique_ptr<QgsCompoundCurve> result( createEmptyWithSameType() );
 
   for ( QgsCurve *curve : mCurves )
   {
-    std::unique_ptr<QgsCurve> gridified( static_cast< QgsCurve * >( curve->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing ) ) );
+    std::unique_ptr<QgsCurve> gridified( static_cast< QgsCurve * >( curve->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing, removeRedundantPoints ) ) );
     if ( gridified )
     {
       result->mCurves.append( gridified.release() );

diff --git a/src/core/geometry/qgscompoundcurve.h b/src/core/geometry/qgscompoundcurve.h
@@ -121,7 +121,7 @@ class CORE_EXPORT QgsCompoundCurve: public QgsCurve
     */
     QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const override SIP_FACTORY;
 
-    QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const override SIP_FACTORY;
+    QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const override SIP_FACTORY;
     bool removeDuplicateNodes( double epsilon = 4 * std::numeric_limits<double>::epsilon(), bool useZValues = false ) override;
     bool boundingBoxIntersects( const QgsBox3D &box3d ) const override SIP_HOLDGIL;
     const QgsAbstractGeometry *simplifiedTypeRef() const override SIP_HOLDGIL;

diff --git a/src/core/geometry/qgscurvepolygon.cpp b/src/core/geometry/qgscurvepolygon.cpp
@@ -551,7 +551,7 @@ QgsAbstractGeometry *QgsCurvePolygon::boundary() const
   }
 }
 
-QgsCurvePolygon *QgsCurvePolygon::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
+QgsCurvePolygon *QgsCurvePolygon::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool removeRedundantPoints ) const
 {
   if ( !mExteriorRing )
     return nullptr;
@@ -560,7 +560,7 @@ QgsCurvePolygon *QgsCurvePolygon::snappedToGrid( double hSpacing, double vSpacin
   std::unique_ptr< QgsCurvePolygon > polygon( createEmptyWithSameType() );
 
   // exterior ring
-  auto exterior = std::unique_ptr<QgsCurve> { static_cast< QgsCurve *>( mExteriorRing->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing ) ) };
+  auto exterior = std::unique_ptr<QgsCurve> { static_cast< QgsCurve *>( mExteriorRing->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing, removeRedundantPoints ) ) };
 
   if ( !exterior )
     return nullptr;
@@ -573,7 +573,7 @@ QgsCurvePolygon *QgsCurvePolygon::snappedToGrid( double hSpacing, double vSpacin
     if ( !interior )
       continue;
 
-    QgsCurve *gridifiedInterior = static_cast< QgsCurve * >( interior->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing ) );
+    QgsCurve *gridifiedInterior = static_cast< QgsCurve * >( interior->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing, removeRedundantPoints ) );
 
     if ( !gridifiedInterior )
       continue;

diff --git a/src/core/geometry/qgscurvepolygon.h b/src/core/geometry/qgscurvepolygon.h
@@ -137,7 +137,7 @@ class CORE_EXPORT QgsCurvePolygon: public QgsSurface
     double perimeter() const override SIP_HOLDGIL;
     QgsPolygon *surfaceToPolygon() const override SIP_FACTORY;
     QgsAbstractGeometry *boundary() const override SIP_FACTORY;
-    QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const override SIP_FACTORY;
+    QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const override SIP_FACTORY;
     bool removeDuplicateNodes( double epsilon = 4 * std::numeric_limits<double>::epsilon(), bool useZValues = false ) override;
     bool boundingBoxIntersects( const QgsBox3D &box3d ) const override SIP_HOLDGIL;
 

diff --git a/src/core/geometry/qgsgeometrycollection.cpp b/src/core/geometry/qgsgeometrycollection.cpp
@@ -92,13 +92,13 @@ void QgsGeometryCollection::clear()
   clearCache(); //set bounding box invalid
 }
 
-QgsGeometryCollection *QgsGeometryCollection::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
+QgsGeometryCollection *QgsGeometryCollection::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool removeRedundantPoints ) const
 {
   std::unique_ptr<QgsGeometryCollection> result;
 
   for ( auto geom : mGeometries )
   {
-    std::unique_ptr<QgsAbstractGeometry> gridified { geom->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing ) };
+    std::unique_ptr<QgsAbstractGeometry> gridified { geom->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing, removeRedundantPoints ) };
     if ( gridified )
     {
       if ( !result )

diff --git a/src/core/geometry/qgsgeometrycollection.h b/src/core/geometry/qgsgeometrycollection.h
@@ -184,7 +184,7 @@ class CORE_EXPORT QgsGeometryCollection: public QgsAbstractGeometry
     int dimension() const override SIP_HOLDGIL;
     QString geometryType() const override SIP_HOLDGIL;
     void clear() override;
-    QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const override SIP_FACTORY;
+    QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0, bool removeRedundantPoints = false ) const override SIP_FACTORY;
     bool removeDuplicateNodes( double epsilon = 4 * std::numeric_limits<double>::epsilon(), bool useZValues = false ) override;
     QgsAbstractGeometry *boundary() const override SIP_FACTORY;
     void adjacentVertices( QgsVertexId vertex, QgsVertexId &previousVertex SIP_OUT, QgsVertexId &nextVertex SIP_OUT ) const override;

diff --git a/src/core/geometry/qgslinestring.cpp b/src/core/geometry/qgslinestring.cpp
@@ -326,7 +326,7 @@ bool QgsLineString::isValid( QString &error, Qgis::GeometryValidityFlags flags )
   return QgsCurve::isValid( error, flags );
 }
 
-QgsLineString *QgsLineString::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
+QgsLineString *QgsLineString::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool removeRedundantPoints ) const
 {
   const int length = numPoints();
   if ( length < 2 )
@@ -355,6 +355,7 @@ QgsLineString *QgsLineString::snappedToGrid( double hSpacing, double vSpacing, d
   double previousY = 0;
   double previousZ = 0;
   double previousM = 0;
+  int outSize = 0;
   for ( int i = 0; i < length; ++i )
   {
     const double currentX = *xIn++;
@@ -375,22 +376,51 @@ QgsLineString *QgsLineString::snappedToGrid( double hSpacing, double vSpacing, d
                                 && ( !hasM || mSpacing <= 0 || qgsDoubleNear( roundedM, previousM ) );
       if ( isPointEqual )
         continue;
-    }
 
-    outX.append( roundedX );
-    outY.append( roundedY );
-    if ( hasZ )
-      outZ.append( roundedZ );
-    if ( hasM )
-      outM.append( roundedM );
+      // maybe previous point is redundant and is just a midpoint on a straight line -- let's check
+      bool previousPointRedundant = false;
+      if ( outSize > 1 && !hasZ && !hasM )
+      {
+        previousPointRedundant = QgsGeometryUtilsBase::leftOfLine( outX.at( outSize - 1 ),
+                                 outY.at( outSize - 1 ),
+                                 outX.at( outSize - 2 ),
+                                 outY.at( outSize - 2 ),
+                                 roundedX, roundedY ) == 0;
+      }
+      if ( previousPointRedundant )
+      {
+        outX[ outSize - 1 ] = roundedX;
+        outY[ outSize - 1 ] = roundedY;
+      }
+      else
+      {
+        outX.append( roundedX );
+        outY.append( roundedY );
+        if ( hasZ )
+          outZ.append( roundedZ );
+        if ( hasM )
+          outM.append( roundedM );
+        outSize++;
+      }
+    }
+    else
+    {
+      outX.append( roundedX );
+      outY.append( roundedY );
+      if ( hasZ )
+        outZ.append( roundedZ );
+      if ( hasM )
+        outM.append( roundedM );
+      outSize++;
+    }
 
     previousX = roundedX;
     previousY = roundedY;
     previousZ = roundedZ;
     previousM = roundedM;
   }
 
-  if ( outX.length() < 2 || ( isClosed() && outX.length() < 4 ) )
+  if ( outSize < 2 || ( isClosed() && outSize < 4 ) )
     return nullptr;
 
   return new QgsLineString( outX, outY, outZ, outM );