Compute min/max on demand in gdal provider

qgis · Feb 19, 2013 · 4d86888 · 4d86888
1 parent 2a2465e
commit 4d86888
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Showing 2 changed files with 16 additions and 6 deletions.
diff --git a/src/providers/gdal/qgsgdalprovider.cpp b/src/providers/gdal/qgsgdalprovider.cpp
@@ -787,7 +787,7 @@ double  QgsGdalProvider::noDataValue() const
 }
 #endif
 
-void QgsGdalProvider::computeMinMax( int theBandNo )
+void QgsGdalProvider::computeMinMax( int theBandNo ) const
 {
   QgsDebugMsg( QString( "theBandNo = %1 mMinMaxComputed = %2" ).arg( theBandNo ).arg( mMinMaxComputed[theBandNo-1] ) );
   if ( mMinMaxComputed[theBandNo-1] )
@@ -810,11 +810,22 @@ void QgsGdalProvider::computeMinMax( int theBandNo )
 double  QgsGdalProvider::minimumValue( int theBandNo ) const
 {
   QgsDebugMsg( QString( "theBandNo = %1" ).arg( theBandNo ) );
+  if ( !mMinMaxComputed[theBandNo-1] )
+  {
+    computeMinMax( theBandNo );
+    mMinMaxComputed[theBandNo-1] = true;
+  }
   return  mMinimum[theBandNo-1];
 }
 double  QgsGdalProvider::maximumValue( int theBandNo ) const
 {
   QgsDebugMsg( QString( "theBandNo = %1" ).arg( theBandNo ) );
+  if ( !mMinMaxComputed[theBandNo-1] )
+  {
+    computeMinMax( theBandNo );
+    mMinMaxComputed[theBandNo-1] = true;
+  }
+  computeMinMax( theBandNo );
   return  mMaximum[theBandNo-1];
 }
 
@@ -2341,7 +2352,6 @@ void QgsGdalProvider::initBaseDataset()
   //mValidNoDataValue = true;
   for ( int i = 1; i <= GDALGetRasterCount( mGdalBaseDataset ); i++ )
   {
-    computeMinMax( i );
     GDALRasterBandH myGdalBand = GDALGetRasterBand( mGdalDataset, i );
     GDALDataType myGdalDataType = GDALGetRasterDataType( myGdalBand );
 

diff --git a/src/providers/gdal/qgsgdalprovider.h b/src/providers/gdal/qgsgdalprovider.h
@@ -179,7 +179,7 @@ class QgsGdalProvider : public QgsRasterDataProvider, QgsGdalProviderBase
 
     //bool srcHasNoDataValue( int bandNo ) const;
     //double noDataValue() const;
-    void computeMinMax( int bandNo );
+    void computeMinMax( int bandNo ) const;
     double minimumValue( int bandNo ) const;
     double maximumValue( int bandNo ) const;
 
@@ -294,13 +294,13 @@ class QgsGdalProvider : public QgsRasterDataProvider, QgsGdalProviderBase
     int mXBlockSize;
     int mYBlockSize;
 
-    QList<bool> mMinMaxComputed;
+    mutable QList<bool> mMinMaxComputed;
 
     // List of estimated min values, index 0 for band 1
-    QList<double> mMinimum;
+    mutable QList<double> mMinimum;
 
     // List of estimated max values, index 0 for band 1
-    QList<double> mMaximum;
+    mutable QList<double> mMaximum;
 
     /** \brief Pointer to the gdaldataset */
     GDALDatasetH mGdalBaseDataset;