Improvements to single band gray renderer widget

src/core/raster/qgsrasterlayer.cpp

@@ -646,20 +646,21 @@ void QgsRasterLayer::setRendererForDrawingStyle( const DrawingStyle &  theDrawin
     {
       int grayBand = bandNumber( mGrayBandName );
       renderer = new QgsSingleBandGrayRenderer( mDataProvider, grayBand );
+      QgsContrastEnhancement* ce = new QgsContrastEnhancement(( QgsContrastEnhancement::QgsRasterDataType )(
+            mDataProvider->dataType( grayBand ) ) );
+      ce->setContrastEnhancementAlgorithm( contrastEnhancementAlgorithm() );
       if ( QgsContrastEnhancement::NoEnhancement != contrastEnhancementAlgorithm() && !mUserDefinedGrayMinimumMaximum && mStandardDeviations > 0 )
       {
-        mGrayMinimumMaximumEstimated = false;
         QgsRasterBandStats myGrayBandStats = bandStatistics( grayBand );
-        setMaximumValue( grayBand, myGrayBandStats.mean + ( mStandardDeviations * myGrayBandStats.stdDev ) );
-        setMinimumValue( grayBand, myGrayBandStats.mean - ( mStandardDeviations * myGrayBandStats.stdDev ) );
+        ce->setMinimumValue( myGrayBandStats.mean - ( mStandardDeviations * myGrayBandStats.stdDev ) );
+        ce->setMaximumValue( myGrayBandStats.mean + ( mStandardDeviations * myGrayBandStats.stdDev ) );
       }
       else if ( QgsContrastEnhancement::NoEnhancement != contrastEnhancementAlgorithm() && !mUserDefinedGrayMinimumMaximum )
       {
-        mGrayMinimumMaximumEstimated = true;
-        setMaximumValue( grayBand, mDataProvider->maximumValue( grayBand ) );
-        setMinimumValue( grayBand, mDataProvider->minimumValue( grayBand ) );
+        ce->setMinimumValue( mDataProvider->minimumValue( grayBand ) );
+        ce->setMaximumValue( mDataProvider->maximumValue( grayBand ) );
       }
-      (( QgsSingleBandGrayRenderer* )renderer )->setContrastEnhancement( contrastEnhancement( grayBand ) );
+      (( QgsSingleBandGrayRenderer* )renderer )->setContrastEnhancement( ce );
       break;
     }
     case SingleBandPseudoColor:

src/gui/raster/qgssinglebandgrayrendererwidget.cpp

@@ -79,8 +79,8 @@ QgsRasterRenderer* QgsSingleBandGrayRendererWidget::renderer()
 
   QgsContrastEnhancement* e = new QgsContrastEnhancement(( QgsContrastEnhancement::QgsRasterDataType )(
         provider->dataType( band ) ) );
-  e->setMinimumValue( mMinLineEdit->text().toInt() );
-  e->setMaximumValue( mMaxLineEdit->text().toInt() );
+  e->setMinimumValue( mMinLineEdit->text().toDouble() );
+  e->setMaximumValue( mMaxLineEdit->text().toDouble() );
   e->setContrastEnhancementAlgorithm(( QgsContrastEnhancement::ContrastEnhancementAlgorithm )( mContrastEnhancementComboBox->itemData(
                                        mContrastEnhancementComboBox->currentIndex() ).toInt() ) );
 
@@ -89,3 +89,45 @@ QgsRasterRenderer* QgsSingleBandGrayRendererWidget::renderer()
   renderer->setContrastEnhancement( e );
   return renderer;
 }
+
+void QgsSingleBandGrayRendererWidget::on_mLoadPushButton_clicked()
+{
+  if ( !mRasterLayer )
+  {
+    return;
+  }
+  QgsRasterDataProvider* provider = mRasterLayer->dataProvider();
+  if ( !provider )
+  {
+    return;
+  }
+
+  int band = mGrayBandComboBox->itemData( mGrayBandComboBox->currentIndex() ).toInt();
+  double minVal = 0;
+  double maxVal = 0;
+  if ( mEstimateRadioButton->isChecked() )
+  {
+    minVal = provider->minimumValue( band );
+    maxVal = provider->maximumValue( band );
+  }
+  else if ( mActualRadioButton->isChecked() )
+  {
+    QgsRasterBandStats rasterBandStats = mRasterLayer->bandStatistics( band );
+    minVal = rasterBandStats.minimumValue;
+    maxVal = rasterBandStats.maximumValue;
+  }
+  else if ( mCurrentExtentRadioButton->isChecked() )
+  {
+    double minMax[2];
+    mRasterLayer->computeMinimumMaximumFromLastExtent( band, minMax );
+    minVal = minMax[0];
+    maxVal = minMax[1];
+  }
+  else
+  {
+    return;
+  }
+
+  mMinLineEdit->setText( QString::number( minVal ) );
+  mMaxLineEdit->setText( QString::number( maxVal ) );
+}

src/gui/raster/qgssinglebandgrayrendererwidget.h

@@ -31,6 +31,9 @@ class QgsSingleBandGrayRendererWidget: public QgsRasterRendererWidget, private U
     static QgsRasterRendererWidget* create( QgsRasterLayer* layer ) { return new QgsSingleBandGrayRendererWidget( layer ); }
 
     QgsRasterRenderer* renderer();
+
+  private slots:
+    void on_mLoadPushButton_clicked();
 };
 
 #endif // QGSSINGLEBANDGRAYRENDERERWIDGET_H

src/ui/qgssinglebandgrayrendererwidgetbase.ui

@@ -73,6 +73,9 @@
         <property name="text">
          <string>Estimate (faster)</string>
         </property>
+        <property name="checked">
+         <bool>true</bool>
+        </property>
        </widget>
       </item>
       <item row="0" column="1" colspan="2">