DOC: improving Viewer tutorial

Examples/Tutorials/SimpleViewer.cxx

@@ -93,6 +93,18 @@ int main( int argc, char * argv[] )
   viewer->SetImage(filter->GetOutput());
   // Software Guide : EndCodeSnippet
   
+  //  Software Guide : BeginLatex
+  //
+  // When you open several reader, this is handy to be able to identify 
+  // each one. This can be done using
+  // \code{SetLabel()}.
+  //
+  //  Software Guide : EndLatex 
+  
+  // Software Guide : BeginCodeSnippet
+  viewer->SetLabel(argv[1]);
+  // Software Guide : EndCodeSnippet
+  
   //  Software Guide : BeginLatex
   //
   // We trigger the pipeline execution and the image display