Fix placement of simple markers in cached images

Author: mhugent

src/core/symbology-ng/qgsmarkersymbollayerv2.cpp

@@ -183,8 +183,7 @@ void QgsSimpleMarkerSymbolLayerV2::prepareCache( QgsSymbolV2RenderContext& conte
   // calculate necessary image size for the cache
   double pw = (( mPen.widthF() == 0 ? 1 : mPen.widthF() ) + 1 ) / 2 * 2; // make even (round up); handle cosmetic pen
   int imageSize = (( int ) scaledSize + pw ) / 2 * 2 + 1; //  make image width, height odd; account for pen width
-
-  double center = (( double ) imageSize / 2 ) + 0.5; // add 1/2 pixel for proper rounding when the figure's coordinates are added
+  double center = imageSize / 2.0;
 
   mCache = QImage( QSize( imageSize, imageSize ), QImage::Format_ARGB32_Premultiplied );
   mCache.fill( 0 );