diff --git a/image.cpp b/image.cpp
index aab751bb..6937b9fa 100644
--- a/image.cpp
+++ b/image.cpp
@@ -255,15 +255,6 @@ util::image::buffer<T>::downsample (float factor) const
 
 ///////////////////////////////////////////////////////////////////////////////
 template <typename T>
-size_t
-buffer<T>::offset (point<2,size_t> p) const
-{
-    return dot (stride (), p);
-}
-
-
-//-----------------------------------------------------------------------------
-template <typename T>
 T
 buffer<T>::operator[] (point<2,size_t> p) const
 {
diff --git a/image.hpp b/image.hpp
index 676b4c7f..ff134fec 100644
--- a/image.hpp
+++ b/image.hpp
@@ -61,7 +61,7 @@ namespace util { namespace image {
         size_t s;
 
         //---------------------------------------------------------------------
-        size_t offset (point<2,size_t>) const;
+        constexpr size_t offset (point<2,size_t>) const;
 
         T  operator[] (point<2,size_t>) const;
         T& operator[] (point<2,size_t>);
diff --git a/image.ipp b/image.ipp
index 7bc798b3..b96e2f33 100644
--- a/image.ipp
+++ b/image.ipp
@@ -38,6 +38,15 @@ namespace util { namespace image {
     }
 
 
+    //-------------------------------------------------------------------------
+    template <typename T>
+    constexpr size_t
+    buffer<T>::offset (point<2,size_t> p) const
+    {
+        return dot (stride (), p);
+    }
+
+
     //-------------------------------------------------------------------------
     template <typename T>
     constexpr size_t