-Fix a problem with generating the highest value of contrast enhancement lookup table

-Added min max estimate on loading to prevent full raster stats from being generated to improve loading speed

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@7953 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: ersts

src/core/raster/qgscontrastenhancement.cpp

@@ -48,7 +48,7 @@ QgsContrastEnhancement::QgsContrastEnhancement(QgsRasterDataType theDataType)
   //If the data type is larger than 16-bit do not generate a lookup table
   if(mRasterDataTypeRange <= 65535.0)
   {
-     mLookupTable = new int[static_cast <int>(mRasterDataTypeRange)];
+     mLookupTable = new int[static_cast <int>(mRasterDataTypeRange+1)];
   }
 
 }
@@ -175,8 +175,9 @@ bool QgsContrastEnhancement::generateLookupTable()
     QgsDebugMsg("***MinimumValue : "+ QString::number(mMinimumValue));
     QgsDebugMsg("***MaximumValue : "+ QString::number(mMaximumValue));
     QgsDebugMsg("***mLookupTableOffset : "+ QString::number(mLookupTableOffset));
+    QgsDebugMsg("***mRasterDataTypeRange : "+ QString::number(mRasterDataTypeRange));
   #endif
-  for(int myIterator = 0; myIterator < mRasterDataTypeRange; myIterator++)
+  for(int myIterator = 0; myIterator <= mRasterDataTypeRange; myIterator++)
   {
     mLookupTable[myIterator] = mContrastEnhancementFunction->enhanceValue((double)myIterator - mLookupTableOffset);
   }

src/core/raster/qgsrasterlayer.cpp

@@ -1443,9 +1443,14 @@ void QgsRasterLayer::drawSingleBandGray(QPainter * theQPainter, QgsRasterViewPor
   }
   else if(QgsContrastEnhancement::NO_STRETCH != getContrastEnhancementAlgorithm() && !mUserDefinedGrayMinMaxFlag)
   {
-    myGrayBandStats = getRasterBandStats(theBandNo);
-    setMaximumValue(theBandNo, myGrayBandStats.maxVal);
-    setMinimumValue(theBandNo, myGrayBandStats.minVal);
+    //This case will be true the first time the image is loaded, so just approimate the min max to keep
+    //from calling generate raster band stats
+    double GDALrange[2];
+    GDALComputeRasterMinMax( myGdalBand, 1, GDALrange ); //Approximate
+
+    setMaximumValue(theBandNo, GDALrange[1]);
+    setMinimumValue(theBandNo, GDALrange[0]);
+
   }
 
   QgsDebugMsg("Starting main render loop");
@@ -2078,16 +2083,20 @@ void QgsRasterLayer::drawMultiBandColor(QPainter * theQPainter, QgsRasterViewPor
   }
   else if(QgsContrastEnhancement::NO_STRETCH != getContrastEnhancementAlgorithm() && !mUserDefinedRGBMinMaxFlag)
   {
-    myRedBandStats = getRasterBandStats(myRedBandNo);
-    myGreenBandStats = getRasterBandStats(myGreenBandNo);
-    myBlueBandStats = getRasterBandStats(myBlueBandNo);
+        //This case will be true the first time the image is loaded, so just approimate the min max to keep
+    //from calling generate raster band stats
+    double GDALrange[2];
+    GDALComputeRasterMinMax( myGdalRedBand, 1, GDALrange ); //Approximate
+    setMaximumValue(myRedBandNo, GDALrange[1]);
+    setMinimumValue(myRedBandNo, GDALrange[0]);
 
-    setMaximumValue(myRedBandNo, myRedBandStats.maxVal);
-    setMinimumValue(myRedBandNo, myRedBandStats.minVal);
-    setMaximumValue(myGreenBandNo, myGreenBandStats.maxVal);
-    setMinimumValue(myGreenBandNo, myGreenBandStats.minVal);
-    setMaximumValue(myBlueBandNo, myBlueBandStats.maxVal);
-    setMinimumValue(myBlueBandNo, myBlueBandStats.minVal);
+    GDALComputeRasterMinMax( myGdalGreenBand, 1, GDALrange ); //Approximate
+    setMaximumValue(myGreenBandNo, GDALrange[1]);
+    setMinimumValue(myGreenBandNo, GDALrange[0]);
+    
+    GDALComputeRasterMinMax( myGdalBlueBand, 1, GDALrange ); //Approximate
+    setMaximumValue(myBlueBandNo, GDALrange[1]);
+    setMinimumValue(myBlueBandNo, GDALrange[0]);
   }
 
   //Read and display pixels