diff --git a/openglcanvas.cpp b/openglcanvas.cpp
index 16a2b4873580459edc3f6c6a35b5e4cfbaf9ae1b..a2326e1628cc9259373e875530e48462ee078b67 100644
--- a/openglcanvas.cpp
+++ b/openglcanvas.cpp
@@ -290,6 +290,7 @@ void OpenGLCanvas::initializeGL(){
 #endif // MSC_VER
 
     read_config_file();
+    compute_scale();
     // If the input file does not exist or was not specified.
     struct stat testbuf;
     if(stat(input_image_file,&testbuf)||!strcmp(input_image_file,"")){