copy WMS image if there is user transparency

git-svn-id: http://svn.osgeo.org/qgis/trunk@10267 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: mhugent

src/core/raster/qgsrasterlayer.cpp

@@ -1538,6 +1538,8 @@ bool QgsRasterLayer::draw( QgsRenderContext& rendererContext )
 
     if(mTransparencyLevel != 255) //improve performance if layer transparency not altered
     {
+         QImage* transparentImageCopy = new QImage(*image); //copy image if there is user transparency
+         image = transparentImageCopy;
         int myWidth = image->width();
         int myHeight = image->height();
         QRgb myRgb;
@@ -1569,6 +1571,11 @@ bool QgsRasterLayer::draw( QgsRenderContext& rendererContext )
                             ),
                             *image );
 
+    if(mTransparencyLevel != 255)
+    {
+        delete image;
+    }
+
   }
   else
   {