From 09a4cb0bac5fe8a6c2563f811171804044c60d65 Mon Sep 17 00:00:00 2001
From: Sandro Mani <manisandro@gmail.com>
Date: Tue, 14 Jun 2016 18:36:23 +0200
Subject: [PATCH] Use screen dpi as reference dpi for computing wmts composer
 scale factor

Ref: 813f818caef896a0f3b3e0ebed8436803ee908e4
---
 src/core/raster/qgsrasterdrawer.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/core/raster/qgsrasterdrawer.cpp b/src/core/raster/qgsrasterdrawer.cpp
index e2ec92147c..eeec6957ec 100644
--- a/src/core/raster/qgsrasterdrawer.cpp
+++ b/src/core/raster/qgsrasterdrawer.cpp
@@ -49,7 +49,9 @@ void QgsRasterDrawer::draw( QPainter* p, QgsRasterViewPort* viewPort, const QgsM
 
   if ( ctx && ctx->customRenderFlags().split( ";" ).contains( "composer" ) && isWMTSLayer( mIterator->input() ) ) //wmts case, comply with standard pixel size of 0.28mm from specification
   {
-    scaleFactor = ( 1.0 / 0.28 * 25.4 ) / p->device()->logicalDpiX();
+    QImage image( 1, 1, QImage::Format_ARGB32 );
+    scaleFactor = double( image.logicalDpiX() ) / p->device()->logicalDpiX();
+    QgsDebugMsg( QString( "Scale factor: %1 (device DPI: %2)" ).arg( scaleFactor ).arg( p->device()->logicalDpiX() ) );
     width = width * scaleFactor;
     height = height * scaleFactor;
     mapToPixel.setParameters( ctx->extent().width() / width, ctx->extent().xMinimum(), ctx->extent().yMinimum(), height );