[FEATURE] allow starting/ending a gradient at a features centroid

python/core/symbology-ng/qgsfillsymbollayerv2.sip

@@ -118,8 +118,6 @@ class QgsGradientFillSymbolLayerV2 : QgsFillSymbolLayerV2
 
     QgsSymbolLayerV2* clone() const /Factory/;
 
-//up to here
-
     GradientType gradientType() const;
     void setGradientType( GradientType gradientType );
 
@@ -140,9 +138,15 @@ class QgsGradientFillSymbolLayerV2 : QgsFillSymbolLayerV2
 
     void setReferencePoint1( QPointF referencePoint );
     QPointF referencePoint1() const;
+    
+    void setReferencePoint1IsCentroid( bool isCentroid );
+    bool referencePoint1IsCentroid() const;
 
     void setReferencePoint2( QPointF referencePoint );
     QPointF referencePoint2() const;
+    
+    void setReferencePoint2IsCentroid( bool isCentroid );
+    bool referencePoint2IsCentroid() const;    
 
     void setAngle( double angle );
     double angle() const;

src/core/symbology-ng/qgsfillsymbollayerv2.cpp

@@ -294,7 +294,9 @@ QgsGradientFillSymbolLayerV2::QgsGradientFillSymbolLayerV2( QColor color, QColor
     mCoordinateMode( coordinateMode ),
     mGradientSpread( spread ),
     mReferencePoint1( QPointF( 0, 0 ) ),
+    mReferencePoint1IsCentroid( false ),
     mReferencePoint2( QPointF( 1, 1 ) ),
+    mReferencePoint2IsCentroid( false ),
     mAngle( 0 ),
     mOffsetUnit( QgsSymbolV2::MM )
 {
@@ -317,7 +319,9 @@ QgsSymbolLayerV2* QgsGradientFillSymbolLayerV2::create( const QgsStringMap& prop
   //default to gradient from the default fill color to white
   QColor color = DEFAULT_SIMPLEFILL_COLOR, color2 = Qt::white;
   QPointF referencePoint1 = QPointF( 0, 0 );
+  bool refPoint1IsCentroid = false;
   QPointF referencePoint2 = QPointF( 1, 1 );
+  bool refPoint2IsCentroid = false;
   double angle = 0;
   QPointF offset;
 
@@ -336,8 +340,12 @@ QgsSymbolLayerV2* QgsGradientFillSymbolLayerV2::create( const QgsStringMap& prop
     color2 = QgsSymbolLayerV2Utils::decodeColor( props["gradient_color2"] );
   if ( props.contains( "reference_point1" ) )
     referencePoint1 = QgsSymbolLayerV2Utils::decodePoint( props["reference_point1"] );
+  if ( props.contains( "reference_point1_iscentroid" ) )
+    refPoint1IsCentroid = props["reference_point1_iscentroid"].toInt();
   if ( props.contains( "reference_point2" ) )
     referencePoint2 = QgsSymbolLayerV2Utils::decodePoint( props["reference_point2"] );
+  if ( props.contains( "reference_point2_iscentroid" ) )
+    refPoint2IsCentroid = props["reference_point2_iscentroid"].toInt();
   if ( props.contains( "angle" ) )
     angle = props["angle"].toDouble();
   if ( props.contains( "offset" ) )
@@ -352,7 +360,9 @@ QgsSymbolLayerV2* QgsGradientFillSymbolLayerV2::create( const QgsStringMap& prop
   if ( props.contains( "offset_unit" ) )
     sl->setOffsetUnit( QgsSymbolLayerV2Utils::decodeOutputUnit( props["offset_unit"] ) );
   sl->setReferencePoint1( referencePoint1 );
+  sl->setReferencePoint1IsCentroid( refPoint1IsCentroid );
   sl->setReferencePoint2( referencePoint2 );
+  sl->setReferencePoint2IsCentroid( refPoint2IsCentroid );
   sl->setAngle( angle );
   if ( gradientRamp )
     sl->setColorRamp( gradientRamp );
@@ -374,10 +384,14 @@ QgsSymbolLayerV2* QgsGradientFillSymbolLayerV2::create( const QgsStringMap& prop
     sl->setDataDefinedProperty( "reference1_x", props["reference1_x_expression"] );
   if ( props.contains( "reference1_y_expression" ) )
     sl->setDataDefinedProperty( "reference1_y", props["reference1_y_expression"] );
+  if ( props.contains( "reference1_iscentroid_expression" ) )
+    sl->setDataDefinedProperty( "reference1_iscentroid", props["reference1_iscentroid_expression"] );
   if ( props.contains( "reference2_x_expression" ) )
     sl->setDataDefinedProperty( "reference2_x", props["reference2_x_expression"] );
   if ( props.contains( "reference2_y_expression" ) )
     sl->setDataDefinedProperty( "reference2_y", props["reference2_y_expression"] );
+  if ( props.contains( "reference2_iscentroid_expression" ) )
+    sl->setDataDefinedProperty( "reference2_iscentroid", props["reference2_iscentroid_expression"] );
 
   return sl;
 }
@@ -393,7 +407,7 @@ QString QgsGradientFillSymbolLayerV2::layerType() const
   return "GradientFill";
 }
 
-void QgsGradientFillSymbolLayerV2::applyDataDefinedSymbology( QgsSymbolV2RenderContext& context )
+void QgsGradientFillSymbolLayerV2::applyDataDefinedSymbology( QgsSymbolV2RenderContext& context, const QPolygonF& points )
 {
   //first gradient color
   QgsExpression* colorExpression = expression( "color" );
@@ -493,6 +507,10 @@ void QgsGradientFillSymbolLayerV2::applyDataDefinedSymbology( QgsSymbolV2RenderC
   double refPoint1Y = mReferencePoint1.y();
   if ( ref1YExpression )
     refPoint1Y = ref1YExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toDouble();
+  QgsExpression* ref1IsCentroidExpression = expression( "reference1_iscentroid" );
+  bool refPoint1IsCentroid = mReferencePoint1IsCentroid;
+  if ( ref1IsCentroidExpression )
+    refPoint1IsCentroid = ref1IsCentroidExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toBool();
 
   //reference point 2 x & y
   QgsExpression* ref2XExpression = expression( "reference2_x" );
@@ -503,6 +521,31 @@ void QgsGradientFillSymbolLayerV2::applyDataDefinedSymbology( QgsSymbolV2RenderC
   double refPoint2Y = mReferencePoint2.y();
   if ( ref2YExpression )
     refPoint2Y = ref2YExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toDouble();
+  QgsExpression* ref2IsCentroidExpression = expression( "reference2_iscentroid" );
+  bool refPoint2IsCentroid = mReferencePoint2IsCentroid;
+  if ( ref2IsCentroidExpression )
+    refPoint2IsCentroid = ref2IsCentroidExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toBool();
+
+  if ( refPoint1IsCentroid || refPoint2IsCentroid )
+  {
+    //either the gradient is starting or ending at a centroid, so calculate it
+    QPointF centroid = QgsSymbolLayerV2Utils::polygonCentroid( points );
+    //centroid coordinates need to be scaled to a range [0, 1] relative to polygon bounds
+    QRectF bbox = points.boundingRect();
+    double centroidX = ( centroid.x() - bbox.left() ) / bbox.width();
+    double centroidY = ( centroid.y() - bbox.top() ) / bbox.height();
+
+    if ( refPoint1IsCentroid )
+    {
+      refPoint1X = centroidX;
+      refPoint1Y = centroidY;
+    }
+    if ( refPoint2IsCentroid )
+    {
+      refPoint2X = centroidX;
+      refPoint2Y = centroidY;
+    }
+  }
 
   //update gradient with data defined values
   applyGradient( context, mBrush, color, color2,  mGradientColorType, mGradientRamp, gradientType, coordinateMode,
@@ -545,8 +588,8 @@ void QgsGradientFillSymbolLayerV2::applyGradient( const QgsSymbolV2RenderContext
   fillColor2.setAlphaF( context.alpha() * fillColor2.alphaF() );
 
   //rotate reference points
-  QPointF rotatedReferencePoint1 = rotateReferencePoint( referencePoint1, angle );
-  QPointF rotatedReferencePoint2 = rotateReferencePoint( referencePoint2, angle );
+  QPointF rotatedReferencePoint1 = angle != 0 ? rotateReferencePoint( referencePoint1, angle ) : referencePoint1;
+  QPointF rotatedReferencePoint2 = angle != 0 ? rotateReferencePoint( referencePoint2, angle ) : referencePoint2;
 
   //create a QGradient with the desired properties
   QGradient gradient;
@@ -604,14 +647,11 @@ void QgsGradientFillSymbolLayerV2::applyGradient( const QgsSymbolV2RenderContext
 
 void QgsGradientFillSymbolLayerV2::startRender( QgsSymbolV2RenderContext& context )
 {
-  //update mBrush to use a gradient fill with specified properties
-  applyGradient( context, mBrush, mColor, mColor2,  mGradientColorType, mGradientRamp, mGradientType, mCoordinateMode,
-                 mGradientSpread, mReferencePoint1, mReferencePoint2, mAngle );
-
   QColor selColor = context.renderContext().selectionColor();
   if ( ! selectionIsOpaque ) selColor.setAlphaF( context.alpha() );
   mSelBrush = QBrush( selColor );
 
+  //update mBrush to use a gradient fill with specified properties
   prepareExpressions( context.layer() );
 }
 
@@ -629,7 +669,7 @@ void QgsGradientFillSymbolLayerV2::renderPolygon( const QPolygonF& points, QList
   }
 
   QPen mSelPen;
-  applyDataDefinedSymbology( context );
+  applyDataDefinedSymbology( context, points );
 
   p->setBrush( context.selected() ? mSelBrush : mBrush );
   p->setPen( QPen( Qt::NoPen ) );
@@ -660,7 +700,9 @@ QgsStringMap QgsGradientFillSymbolLayerV2::properties() const
   map["coordinate_mode"] = QString::number( mCoordinateMode );
   map["spread"] = QString::number( mGradientSpread );
   map["reference_point1"] = QgsSymbolLayerV2Utils::encodePoint( mReferencePoint1 );
+  map["reference_point1_iscentroid"] = QString::number( mReferencePoint1IsCentroid );
   map["reference_point2"] = QgsSymbolLayerV2Utils::encodePoint( mReferencePoint2 );
+  map["reference_point2_iscentroid"] = QString::number( mReferencePoint2IsCentroid );
   map["angle"] = QString::number( mAngle );
   map["offset"] = QgsSymbolLayerV2Utils::encodePoint( mOffset );
   map["offset_unit"] = QgsSymbolLayerV2Utils::encodeOutputUnit( mOffsetUnit );
@@ -678,7 +720,9 @@ QgsSymbolLayerV2* QgsGradientFillSymbolLayerV2::clone() const
   if ( mGradientRamp )
     sl->setColorRamp( mGradientRamp->clone() );
   sl->setReferencePoint1( mReferencePoint1 );
+  sl->setReferencePoint1IsCentroid( mReferencePoint1IsCentroid );
   sl->setReferencePoint2( mReferencePoint2 );
+  sl->setReferencePoint2IsCentroid( mReferencePoint2IsCentroid );
   sl->setAngle( mAngle );
   sl->setOffset( mOffset );
   sl->setOffsetUnit( mOffsetUnit );
@@ -2045,23 +2089,8 @@ void QgsCentroidFillSymbolLayerV2::renderPolygon( const QPolygonF& points, QList
 {
   Q_UNUSED( rings );
 
-  // calculate centroid
-  double cx = 0, cy = 0;
-  double area, sum = 0;
-  for ( int i = points.count() - 1, j = 0; j < points.count(); i = j++ )
-  {
-    const QPointF& p1 = points[i];
-    const QPointF& p2 = points[j];
-    area = p1.x() * p2.y() - p1.y() * p2.x();
-    sum += area;
-    cx += ( p1.x() + p2.x() ) * area;
-    cy += ( p1.y() + p2.y() ) * area;
-  }
-  sum *= 3.0;
-  cx /= sum;
-  cy /= sum;
-
-  mMarker->renderPoint( QPointF( cx, cy ), context.feature(), context.renderContext(), -1, context.selected() );
+  QPointF centroid = QgsSymbolLayerV2Utils::polygonCentroid( points );
+  mMarker->renderPoint( centroid, context.feature(), context.renderContext(), -1, context.selected() );
 }
 
 QgsStringMap QgsCentroidFillSymbolLayerV2::properties() const

src/core/symbology-ng/qgsfillsymbollayerv2.h

@@ -188,10 +188,18 @@ class CORE_EXPORT QgsGradientFillSymbolLayerV2 : public QgsFillSymbolLayerV2
     void setReferencePoint1( QPointF referencePoint ) { mReferencePoint1 = referencePoint; };
     QPointF referencePoint1() const { return mReferencePoint1; };
 
+    /**Sets the starting point of the gradient to be the feature centroid*/
+    void setReferencePoint1IsCentroid( bool isCentroid ) { mReferencePoint1IsCentroid = isCentroid; };
+    bool referencePoint1IsCentroid() const { return mReferencePoint1IsCentroid; };
+
     /**End point of gradient fill, in the range [0,0] - [1,1]*/
     void setReferencePoint2( QPointF referencePoint ) { mReferencePoint2 = referencePoint; };
     QPointF referencePoint2() const { return mReferencePoint2; };
 
+    /**Sets the end point of the gradient to be the feature centroid*/
+    void setReferencePoint2IsCentroid( bool isCentroid ) { mReferencePoint2IsCentroid = isCentroid; };
+    bool referencePoint2IsCentroid() const { return mReferencePoint2IsCentroid; };
+
     /**Rotation angle for gradient fill. Can be used to rotate a gradient around its centre point*/
     void setAngle( double angle ) { mAngle = angle; };
     double angle() const { return mAngle; };
@@ -216,7 +224,9 @@ class CORE_EXPORT QgsGradientFillSymbolLayerV2 : public QgsFillSymbolLayerV2
     GradientSpread mGradientSpread;
 
     QPointF mReferencePoint1;
+    bool mReferencePoint1IsCentroid;
     QPointF mReferencePoint2;
+    bool mReferencePoint2IsCentroid;
     double mAngle;
 
     QPointF mOffset;
@@ -225,7 +235,7 @@ class CORE_EXPORT QgsGradientFillSymbolLayerV2 : public QgsFillSymbolLayerV2
   private:
 
     //helper functions for data defined symbology
-    void applyDataDefinedSymbology( QgsSymbolV2RenderContext& context );
+    void applyDataDefinedSymbology( QgsSymbolV2RenderContext& context, const QPolygonF& points );
 
     /**Applies the gradient to a brush*/
     void applyGradient( const QgsSymbolV2RenderContext& context, QBrush& brush, const QColor& color, const QColor& color2,

src/core/symbology-ng/qgssymbollayerv2utils.cpp

@@ -2925,3 +2925,25 @@ QString QgsSymbolLayerV2Utils::symbolPathToName( QString path )
   return QgsProject::instance()->writePath( path );
 }
 
+QPointF QgsSymbolLayerV2Utils::polygonCentroid( const QPolygonF& points )
+{
+  //Calculate the centroid of points
+  double cx = 0, cy = 0;
+  double area, sum = 0;
+  for ( int i = points.count() - 1, j = 0; j < points.count(); i = j++ )
+  {
+    const QPointF& p1 = points[i];
+    const QPointF& p2 = points[j];
+    area = p1.x() * p2.y() - p1.y() * p2.x();
+    sum += area;
+    cx += ( p1.x() + p2.x() ) * area;
+    cy += ( p1.y() + p2.y() ) * area;
+  }
+  sum *= 3.0;
+  cx /= sum;
+  cy /= sum;
+
+  return QPointF( cx, cy );
+}
+
+

src/core/symbology-ng/qgssymbollayerv2utils.h

@@ -243,6 +243,9 @@ class CORE_EXPORT QgsSymbolLayerV2Utils
 
     //! Get symbols's name from its path
     static QString symbolPathToName( QString path );
+
+    //! Calculate the centroid point of a QPolygonF
+    static QPointF polygonCentroid( const QPolygonF& points );
 };
 
 class QPolygonF;

src/gui/symbology-ng/qgsdatadefinedsymboldialog.cpp

@@ -208,4 +208,9 @@ QString QgsDataDefinedSymbolDialog::gradientSpreadHelpText()
   return tr( "'pad'|'repeat'|'reflect'" );
 }
 
+QString QgsDataDefinedSymbolDialog::boolHelpText()
+{
+  return tr( "0 (false)|1 (true)" );
+}
+
 

src/gui/symbology-ng/qgsdatadefinedsymboldialog.h

@@ -38,6 +38,7 @@ class GUI_EXPORT QgsDataDefinedSymbolDialog: public QDialog, private Ui::QgsData
     static QString gradientTypeHelpText();
     static QString gradientCoordModeHelpText();
     static QString gradientSpreadHelpText();
+    static QString boolHelpText();
 
   private slots:
     void expressionButtonClicked();

src/gui/symbology-ng/qgssymbollayerv2widget.cpp

@@ -638,8 +638,10 @@ QgsGradientFillSymbolLayerV2Widget::QgsGradientFillSymbolLayerV2Widget( const Qg
   connect( spinOffsetY, SIGNAL( valueChanged( double ) ), this, SLOT( offsetChanged() ) );
   connect( spinRefPoint1X, SIGNAL( valueChanged( double ) ), this, SLOT( referencePointChanged() ) );
   connect( spinRefPoint1Y, SIGNAL( valueChanged( double ) ), this, SLOT( referencePointChanged() ) );
+  connect( checkRefPoint1Centroid, SIGNAL( toggled( bool ) ), this, SLOT( referencePointChanged() ) );
   connect( spinRefPoint2X, SIGNAL( valueChanged( double ) ), this, SLOT( referencePointChanged() ) );
   connect( spinRefPoint2Y, SIGNAL( valueChanged( double ) ), this, SLOT( referencePointChanged() ) );
+  connect( checkRefPoint2Centroid, SIGNAL( toggled( bool ) ), this, SLOT( referencePointChanged() ) );
 }
 
 void QgsGradientFillSymbolLayerV2Widget::setSymbolLayer( QgsSymbolLayerV2* layer )
@@ -696,6 +698,8 @@ void QgsGradientFillSymbolLayerV2Widget::setSymbolLayer( QgsSymbolLayerV2* layer
   {
     case QgsGradientFillSymbolLayerV2::Viewport:
       cboCoordinateMode->setCurrentIndex( 1 );
+      checkRefPoint1Centroid->setEnabled( false );
+      checkRefPoint2Centroid->setEnabled( false );
       break;
     case QgsGradientFillSymbolLayerV2::Feature:
     default:
@@ -725,12 +729,28 @@ void QgsGradientFillSymbolLayerV2Widget::setSymbolLayer( QgsSymbolLayerV2* layer
   spinRefPoint1Y->blockSignals( true );
   spinRefPoint1Y->setValue( mLayer->referencePoint1().y() );
   spinRefPoint1Y->blockSignals( false );
+  checkRefPoint1Centroid->blockSignals( true );
+  checkRefPoint1Centroid->setChecked( mLayer->referencePoint1IsCentroid() );
+  if ( mLayer->referencePoint1IsCentroid() )
+  {
+    spinRefPoint1X->setEnabled( false );
+    spinRefPoint1Y->setEnabled( false );
+  }
+  checkRefPoint1Centroid->blockSignals( false );
   spinRefPoint2X->blockSignals( true );
   spinRefPoint2X->setValue( mLayer->referencePoint2().x() );
   spinRefPoint2X->blockSignals( false );
   spinRefPoint2Y->blockSignals( true );
   spinRefPoint2Y->setValue( mLayer->referencePoint2().y() );
   spinRefPoint2Y->blockSignals( false );
+  checkRefPoint2Centroid->blockSignals( true );
+  checkRefPoint2Centroid->setChecked( mLayer->referencePoint2IsCentroid() );
+  if ( mLayer->referencePoint2IsCentroid() )
+  {
+    spinRefPoint2X->setEnabled( false );
+    spinRefPoint2Y->setEnabled( false );
+  }
+  checkRefPoint2Centroid->blockSignals( false );
 
   spinOffsetX->blockSignals( true );
   spinOffsetX->setValue( mLayer->offset().x() );
@@ -810,10 +830,20 @@ void QgsGradientFillSymbolLayerV2Widget::setCoordinateMode( int index )
   switch ( index )
   {
     case 0:
+      //feature coordinate mode
       mLayer->setCoordinateMode( QgsGradientFillSymbolLayerV2::Feature );
+      //allow choice of centroid reference positions
+      checkRefPoint1Centroid->setEnabled( true );
+      checkRefPoint2Centroid->setEnabled( true );
       break;
     case 1:
+      //viewport coordinate mode
       mLayer->setCoordinateMode( QgsGradientFillSymbolLayerV2::Viewport );
+      //disable choice of centroid reference positions
+      checkRefPoint1Centroid->setChecked( Qt::Unchecked );
+      checkRefPoint1Centroid->setEnabled( false );
+      checkRefPoint2Centroid->setChecked( Qt::Unchecked );
+      checkRefPoint2Centroid->setEnabled( false );
       break;
   }
 
@@ -847,7 +877,9 @@ void QgsGradientFillSymbolLayerV2Widget::offsetChanged()
 void QgsGradientFillSymbolLayerV2Widget::referencePointChanged()
 {
   mLayer->setReferencePoint1( QPointF( spinRefPoint1X->value(), spinRefPoint1Y->value() ) );
+  mLayer->setReferencePoint1IsCentroid( checkRefPoint1Centroid->isChecked() );
   mLayer->setReferencePoint2( QPointF( spinRefPoint2X->value(), spinRefPoint2Y->value() ) );
+  mLayer->setReferencePoint2IsCentroid( checkRefPoint2Centroid->isChecked() );
   emit changed();
 }
 
@@ -886,10 +918,14 @@ void QgsGradientFillSymbolLayerV2Widget::on_mDataDefinedPropertiesButton_clicked
       QgsDataDefinedSymbolDialog::doubleHelpText() );
   dataDefinedProperties << QgsDataDefinedSymbolDialog::DataDefinedSymbolEntry( "reference1_y", tr( "Reference Point 1 (y)" ), mLayer->dataDefinedPropertyString( "reference1_y" ),
       QgsDataDefinedSymbolDialog::doubleHelpText() );
+  dataDefinedProperties << QgsDataDefinedSymbolDialog::DataDefinedSymbolEntry( "reference1_iscentroid", tr( "Reference Point 1 (is centroid)" ), mLayer->dataDefinedPropertyString( "reference1_iscentroid" ),
+      QgsDataDefinedSymbolDialog::boolHelpText() );
   dataDefinedProperties << QgsDataDefinedSymbolDialog::DataDefinedSymbolEntry( "reference2_x", tr( "Reference Point 2 (x)" ), mLayer->dataDefinedPropertyString( "reference2_x" ),
       QgsDataDefinedSymbolDialog::doubleHelpText() );
   dataDefinedProperties << QgsDataDefinedSymbolDialog::DataDefinedSymbolEntry( "reference2_y", tr( "Reference Point 2 (y)" ), mLayer->dataDefinedPropertyString( "reference2_y" ),
       QgsDataDefinedSymbolDialog::doubleHelpText() );
+  dataDefinedProperties << QgsDataDefinedSymbolDialog::DataDefinedSymbolEntry( "reference2_iscentroid", tr( "Reference Point 2 (is centroid)" ), mLayer->dataDefinedPropertyString( "reference2_iscentroid" ),
+      QgsDataDefinedSymbolDialog::boolHelpText() );
 
   QgsDataDefinedSymbolDialog d( dataDefinedProperties, mVectorLayer );
   if ( d.exec() == QDialog::Accepted )

src/ui/symbollayer/widget_gradientfill.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>474</width>
-    <height>327</height>
+    <height>358</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -189,6 +189,9 @@
    </item>
    <item row="5" column="1">
     <layout class="QHBoxLayout" name="horizontalLayout_6">
+     <property name="spacing">
+      <number>12</number>
+     </property>
      <item>
       <widget class="QLabel" name="label_5">
        <property name="text">
@@ -223,6 +226,26 @@
        </property>
       </widget>
      </item>
+     <item>
+      <widget class="QCheckBox" name="checkRefPoint1Centroid">
+       <property name="text">
+        <string>Feature centroid</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <spacer name="horizontalSpacer_2">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
     </layout>
    </item>
    <item row="7" column="0">
@@ -234,6 +257,9 @@
    </item>
    <item row="7" column="1">
     <layout class="QHBoxLayout" name="horizontalLayout_7">
+     <property name="spacing">
+      <number>12</number>
+     </property>
      <item>
       <widget class="QLabel" name="label_9">
        <property name="text">
@@ -274,6 +300,26 @@
        </property>
       </widget>
      </item>
+     <item>
+      <widget class="QCheckBox" name="checkRefPoint2Centroid">
+       <property name="text">
+        <string>Feature centroid</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <spacer name="horizontalSpacer_3">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
     </layout>
    </item>
    <item row="9" column="0">
@@ -433,5 +479,69 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>checkRefPoint1Centroid</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>spinRefPoint1X</receiver>
+   <slot>setDisabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>400</x>
+     <y>187</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>204</x>
+     <y>188</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>checkRefPoint1Centroid</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>spinRefPoint1Y</receiver>
+   <slot>setDisabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>400</x>
+     <y>187</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>293</x>
+     <y>188</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>checkRefPoint2Centroid</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>spinRefPoint2X</receiver>
+   <slot>setDisabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>400</x>
+     <y>228</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>204</x>
+     <y>229</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>checkRefPoint2Centroid</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>spinRefPoint2Y</receiver>
+   <slot>setDisabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>400</x>
+     <y>228</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>293</x>
+     <y>229</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>

tests/src/core/testqgsgradients.cpp

@@ -56,6 +56,7 @@ class TestQgsGradients: public QObject
     void gradientSymbolConical();
     void gradientSymbolViewport();
     void gradientSymbolReferencePoints();
+    void gradientSymbolCentroid();
     void gradientSymbolReflectSpread();
     void gradientSymbolRepeatSpread();
     void gradientSymbolRotate();
@@ -200,6 +201,17 @@ void TestQgsGradients::gradientSymbolReferencePoints()
   mGradientFill->setReferencePoint2( QPointF( 1, 1 ) );
 }
 
+void TestQgsGradients::gradientSymbolCentroid()
+{
+  mReport += "<h2>Gradient symbol renderer centroid reference point test</h2>\n";
+  mGradientFill->setReferencePoint1IsCentroid( true );
+  QVERIFY( imageCheck( "gradient_ref1centroid" ) );
+  mGradientFill->setReferencePoint1IsCentroid( false );
+  mGradientFill->setReferencePoint2IsCentroid( true );
+  QVERIFY( imageCheck( "gradient_ref2centroid" ) );
+  mGradientFill->setReferencePoint2IsCentroid( false );
+}
+
 void TestQgsGradients::gradientSymbolReflectSpread()
 {
   mReport += "<h2>Gradient symbol renderer reflect spread test</h2>\n";

tests/src/python/test_qgssymbollayerv2.py

@@ -295,12 +295,24 @@ class TestQgsSymbolLayerV2(TestCase):
         mMessage = 'Expected "%s" got "%s"' % (mExpectedValue,mValue)
         assert mExpectedValue == mValue, mMessage
 
+        mExpectedValue = True
+        mGradientLayer.setReferencePoint1IsCentroid( mExpectedValue )
+        mValue = mGradientLayer.referencePoint1IsCentroid()
+        mMessage = 'Expected "%s" got "%s"' % (mExpectedValue,mValue)
+        assert mExpectedValue == mValue, mMessage
+
         mExpectedValue = QPointF(0.2, 0.4)
         mGradientLayer.setReferencePoint2( mExpectedValue )
         mValue = mGradientLayer.referencePoint2()
         mMessage = 'Expected "%s" got "%s"' % (mExpectedValue,mValue)
         assert mExpectedValue == mValue, mMessage
 
+        mExpectedValue = True
+        mGradientLayer.setReferencePoint2IsCentroid( mExpectedValue )
+        mValue = mGradientLayer.referencePoint2IsCentroid()
+        mMessage = 'Expected "%s" got "%s"' % (mExpectedValue,mValue)
+        assert mExpectedValue == mValue, mMessage
+
         mExpectedValue = 90
         mGradientLayer.setAngle( mExpectedValue )
         mValue = mGradientLayer.angle()