[BACKPORT] set default contrast enchacement algorithm to NoStretch

(addresses #3867). Also set default standard deviations value to 2.0
because this is more appropriate value

Author: alexbruy

src/app/qgsrasterlayerproperties.cpp

@@ -756,7 +756,7 @@ void QgsRasterLayerProperties::sync()
     {
       labelDefaultContrastEnhancementAlgorithm->setText( tr( "No Stretch" ) );
     }
-    mDefaultStandardDeviation = myQSettings.value( "/Raster/defaultStandardDeviation", 1.0 ).toDouble();
+    mDefaultStandardDeviation = myQSettings.value( "/Raster/defaultStandardDeviation", 2.0 ).toDouble();
     sboxThreeBandStdDev->setValue( mDefaultStandardDeviation );
   }
 

src/core/raster/qgsrasterlayer.cpp

@@ -2364,7 +2364,7 @@ void QgsRasterLayer::setDataProvider( QString const & provider,
   //Try to read the default contrast enhancement from the config file
 
   QSettings myQSettings;
-  setContrastEnhancementAlgorithm( myQSettings.value( "/Raster/defaultContrastEnhancementAlgorithm", "StretchToMinimumMaximum" ).toString() );
+  setContrastEnhancementAlgorithm( myQSettings.value( "/Raster/defaultContrastEnhancementAlgorithm", "NoEnhancement" ).toString() );
 
   //decide what type of layer this is...
   //TODO Change this to look at the color interp and palette interp to decide which type of layer it is
@@ -2461,7 +2461,7 @@ void QgsRasterLayer::setDataProvider( QString const & provider,
     // read standard deviations
     if ( mContrastEnhancementAlgorithm == QgsContrastEnhancement::StretchToMinimumMaximum )
     {
-      setStandardDeviations( myQSettings.value( "/Raster/defaultStandardDeviation", 1.0 ).toInt() );
+      setStandardDeviations( myQSettings.value( "/Raster/defaultStandardDeviation", 2.0 ).toInt() );
     }
   }
   else                        //GrayOrUndefined
@@ -2476,7 +2476,7 @@ void QgsRasterLayer::setDataProvider( QString const & provider,
     // read standard deviations
     if ( mContrastEnhancementAlgorithm == QgsContrastEnhancement::StretchToMinimumMaximum )
     {
-      setStandardDeviations( myQSettings.value( "/Raster/defaultStandardDeviation", 1.0 ).toInt() );
+      setStandardDeviations( myQSettings.value( "/Raster/defaultStandardDeviation", 2.0 ).toInt() );
     }
   }
   // Debug