COMP: Removing conversion warning

Change-Id: I9d97735cf72bae96b9a693c0eb0527dc6c8eeb45

Infovis/vtkGraphAnnotationLayersFilter.cxx

@@ -220,8 +220,11 @@ int vtkGraphAnnotationLayersFilter::RequestData(vtkInformation *vtkNotUsed(reque
       outColors->SetName("Hull color");
       double* color = annotation->GetInformation()->Get(vtkAnnotation::COLOR());
       double opacity = annotation->GetInformation()->Get(vtkAnnotation::OPACITY());
-      unsigned char outColor[4] = { color[0] * 255, color[1] * 255,
-        color[2] * 255, opacity * 255 };
+      unsigned char outColor[4] = {
+        static_cast<unsigned char>(color[0] * 255), 
+        static_cast<unsigned char>(color[1] * 255),
+        static_cast<unsigned char>(color[2] * 255),
+        static_cast<unsigned char>(opacity * 255) };
       for (vtkIdType i = 0; i < numberOfCells; ++i)
         {
         outColors->InsertNextTupleValue(outColor);