From 5ee5a17a28cfc784a3e995e0f05b2e66f5c33719 Mon Sep 17 00:00:00 2001
From: Marco Hugentobler <marco.hugentobler@sourcepole.ch>
Date: Tue, 3 Jan 2012 11:16:28 +0100
Subject: [PATCH] Detect if transparency can be ignored for paletted renderer

---
 src/core/raster/qgspalettedrasterrenderer.cpp |  4 +++-
 src/core/raster/qgsrasterrenderer.cpp         | 10 ++++++++--
 src/core/raster/qgsrasterrenderer.h           |  2 +-
 src/core/raster/qgsrastertransparency.cpp     | 11 +++++++++--
 src/core/raster/qgsrastertransparency.h       |  4 ++--
 5 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/src/core/raster/qgspalettedrasterrenderer.cpp b/src/core/raster/qgspalettedrasterrenderer.cpp
index 0e6519572958..e09957c1776c 100644
--- a/src/core/raster/qgspalettedrasterrenderer.cpp
+++ b/src/core/raster/qgspalettedrasterrenderer.cpp
@@ -17,6 +17,7 @@
 
 #include "qgspalettedrasterrenderer.h"
 #include "qgsrastertransparency.h"
+#include "qgsrasterviewport.h"
 #include <QColor>
 #include <QImage>
 
@@ -61,7 +62,8 @@ void QgsPalettedRasterRenderer::draw( QPainter* p, QgsRasterViewPort* viewPort,
   void* rasterData;
   double currentOpacity = mOpacity;
 
-  bool hasTransparency = usesTransparency();
+  //rendering is faster without considering user-defined transparency
+  bool hasTransparency = usesTransparency( viewPort->mSrcCRS, viewPort->mDestCRS );
   void* transparencyData;
 
   while ( readNextRasterPart( mBandNumber, viewPort, nCols, nRows, &rasterData, topLeftCol, topLeftRow ) )
diff --git a/src/core/raster/qgsrasterrenderer.cpp b/src/core/raster/qgsrasterrenderer.cpp
index c3f73f3b7c6b..876e606eaabf 100644
--- a/src/core/raster/qgsrasterrenderer.cpp
+++ b/src/core/raster/qgsrasterrenderer.cpp
@@ -157,9 +157,15 @@ void QgsRasterRenderer::removePartInfo( int bandNumber )
   }
 }
 
-bool QgsRasterRenderer::usesTransparency() const
+bool QgsRasterRenderer::usesTransparency( QgsCoordinateReferenceSystem& srcSRS, QgsCoordinateReferenceSystem& dstSRS ) const
 {
-  return ( mAlphaBand > 0 || ( mRasterTransparency && !mRasterTransparency->isEmpty() ) || !doubleNear( mOpacity, 1.0 ) );
+  //transparency is always used if on-the-fly reprojection is enabled
+  bool reprojectionEnabled = ( srcSRS.isValid() && dstSRS.isValid() && srcSRS != dstSRS );
+  if ( !mProvider || reprojectionEnabled )
+  {
+    return true;
+  }
+  return ( mAlphaBand > 0 || ( mRasterTransparency && !mRasterTransparency->isEmpty( mProvider->noDataValue() ) ) || !doubleNear( mOpacity, 1.0 ) );
 }
 
 void QgsRasterRenderer::drawImage( QPainter* p, QgsRasterViewPort* viewPort, const QImage& img, int topLeftCol, int topLeftRow,
diff --git a/src/core/raster/qgsrasterrenderer.h b/src/core/raster/qgsrasterrenderer.h
index 839621b7ec5c..42c565b41fcd 100644
--- a/src/core/raster/qgsrasterrenderer.h
+++ b/src/core/raster/qgsrasterrenderer.h
@@ -45,7 +45,7 @@ class QgsRasterRenderer
     virtual ~QgsRasterRenderer();
     virtual void draw( QPainter* p, QgsRasterViewPort* viewPort, const QgsMapToPixel* theQgsMapToPixel ) = 0;
 
-    bool usesTransparency() const;
+    bool usesTransparency( QgsCoordinateReferenceSystem& srcSRS, QgsCoordinateReferenceSystem& dstSRS ) const;
 
     void setOpacity( double opacity ) { mOpacity = opacity; }
     double opacity() const { return mOpacity; }
diff --git a/src/core/raster/qgsrastertransparency.cpp b/src/core/raster/qgsrastertransparency.cpp
index c86aa3035823..b4e7861da411 100644
--- a/src/core/raster/qgsrastertransparency.cpp
+++ b/src/core/raster/qgsrastertransparency.cpp
@@ -18,6 +18,7 @@ email                : ersts@amnh.org
 #include <QList>
 
 #include "qgsrastertransparency.h"
+#include "qgis.h"
 
 QgsRasterTransparency::QgsRasterTransparency()
 {
@@ -169,7 +170,13 @@ int QgsRasterTransparency::alphaValue( double theRedValue, double theGreenValue,
   return theGlobalTransparency;
 }
 
-bool QgsRasterTransparency::isEmpty() const
+bool QgsRasterTransparency::isEmpty( double nodataValue ) const
 {
-  return ( mTransparentThreeValuePixelList.isEmpty() && mTransparentSingleValuePixelList.isEmpty() );
+  return (
+           ( mTransparentSingleValuePixelList.isEmpty() ||
+             ( mTransparentSingleValuePixelList.size() == 1 && doubleNear( mTransparentSingleValuePixelList.at( 0 ).pixelValue, nodataValue ) ) )
+           &&
+           ( mTransparentThreeValuePixelList.isEmpty() ||
+             ( mTransparentThreeValuePixelList.size() == 1 && doubleNear( mTransparentThreeValuePixelList.at( 0 ).red, nodataValue ) &&
+               doubleNear( mTransparentThreeValuePixelList.at( 0 ).green, nodataValue ) && doubleNear( mTransparentThreeValuePixelList.at( 0 ).blue, nodataValue ) ) ) );
 }
diff --git a/src/core/raster/qgsrastertransparency.h b/src/core/raster/qgsrastertransparency.h
index e79a92de1749..966301c524be 100644
--- a/src/core/raster/qgsrastertransparency.h
+++ b/src/core/raster/qgsrastertransparency.h
@@ -72,8 +72,8 @@ class CORE_EXPORT QgsRasterTransparency
     /** \brief Return the transparency value for a RGB Pixel */
     int alphaValue( double, double, double, int theGlobalTransparency = 255 ) const;
 
-    /**True if there are no entries in the pixel lists*/
-    bool isEmpty() const;
+    /**True if there are no entries in the pixel lists except the nodata value*/
+    bool isEmpty( double nodataValue ) const;
 
   private:
     /** \brief The list to hold transparency values for RGB layers */