Speed up map to pixel simplification by directly accessing x/y vertex…

… data
qgis · May 26, 2018 · 80e44c1 · 80e44c1
1 parent e6a0d52
commit 80e44c1
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Showing 4 changed files with 64 additions and 4 deletions.
diff --git a/python/core/auto_generated/geometry/qgslinestring.sip.in b/python/core/auto_generated/geometry/qgslinestring.sip.in
@@ -87,6 +87,8 @@ Returns the specified point from inside the line string.
     virtual double yAt( int index ) const;
 
 
+
+
     double zAt( int index ) const;
 %Docstring
 Returns the z-coordinate of the specified node in the line string.

diff --git a/src/core/geometry/qgslinestring.cpp b/src/core/geometry/qgslinestring.cpp
@@ -535,6 +535,16 @@ double QgsLineString::yAt( int index ) const
     return 0.0;
 }
 
+const double *QgsLineString::xData() const
+{
+  return mX.constData();
+}
+
+const double *QgsLineString::yData() const
+{
+  return mY.constData();
+}
+
 double QgsLineString::zAt( int index ) const
 {
   if ( index >= 0 && index < mZ.size() )

diff --git a/src/core/geometry/qgslinestring.h b/src/core/geometry/qgslinestring.h
@@ -96,6 +96,22 @@ class CORE_EXPORT QgsLineString: public QgsCurve
     double xAt( int index ) const override;
     double yAt( int index ) const override;
 
+    /**
+     * Returns a const pointer to the x vertex data.
+     * \since QGIS 3.2
+     * \note Not available in Python bindings
+     * \see yData()
+     */
+    const double *xData() const SIP_SKIP;
+
+    /**
+     * Returns a const pointer to the y vertex data.
+     * \since QGIS 3.2
+     * \note Not available in Python bindings
+     * \see xData()
+     */
+    const double *yData() const SIP_SKIP;
+
     /**
      * Returns the z-coordinate of the specified node in the line string.
      * \param index index of node, where the first node in the line is 0

diff --git a/src/core/qgsmaptopixelgeometrysimplifier.cpp b/src/core/qgsmaptopixelgeometrysimplifier.cpp
@@ -189,10 +189,26 @@ std::unique_ptr< QgsAbstractGeometry > QgsMapToPixelSimplifier::simplifyGeometry
         // Use a factor for the maximum displacement distance for simplification, similar as GeoServer does
         float gridInverseSizeXY = map2pixelTol != 0 ? ( float )( 1.0f / ( 0.8 * map2pixelTol ) ) : 0.0f;
 
+        const double *xData = nullptr;
+        const double *yData = nullptr;
+        if ( flatType == QgsWkbTypes::LineString )
+        {
+          xData = static_cast< const QgsLineString * >( &srcCurve )->xData();
+          yData = static_cast< const QgsLineString * >( &srcCurve )->yData();
+        }
+
         for ( int i = 0; i < numPoints; ++i )
         {
-          x = srcCurve.xAt( i );
-          y = srcCurve.yAt( i );
+          if ( xData && yData )
+          {
+            x = *xData++;
+            y = *yData++;
+          }
+          else
+          {
+            x = srcCurve.xAt( i );
+            y = srcCurve.yAt( i );
+          }
 
           if ( i == 0 ||
                !isGeneralizable ||
@@ -244,10 +260,26 @@ std::unique_ptr< QgsAbstractGeometry > QgsMapToPixelSimplifier::simplifyGeometry
       {
         map2pixelTol *= map2pixelTol; //-> Use mappixelTol for 'LengthSquare' calculations.
 
+        const double *xData = nullptr;
+        const double *yData = nullptr;
+        if ( flatType == QgsWkbTypes::LineString )
+        {
+          xData = static_cast< const QgsLineString * >( &srcCurve )->xData();
+          yData = static_cast< const QgsLineString * >( &srcCurve )->yData();
+        }
+
         for ( int i = 0; i < numPoints; ++i )
         {
-          x = srcCurve.xAt( i );
-          y = srcCurve.yAt( i );
+          if ( xData && yData )
+          {
+            x = *xData++;
+            y = *yData++;
+          }
+          else
+          {
+            x = srcCurve.xAt( i );
+            y = srcCurve.yAt( i );
+          }
 
           isLongSegment = false;