BF: Use volume extrapolation getters rather than fields, as the fields won't

have been initialised on ShadowVolume instances, whereas the getters will
delegate to the owning volume

newimage.h

@@ -207,26 +207,26 @@ int readGeneralVolume(volume<T>& target, const std::string& filename,
 
     public:
       extrapolation method(const volume<T>& vol) const {
-        if (_use_default_method) return vol.p_extrapmethod;
+        if (_use_default_method) return vol.getextrapolationmethod();
         else                     return _method;
       }
       T padvalue(const volume<T>& vol) const {
-        if (_use_default_padvalue) return vol.padvalue;
+        if (_use_default_padvalue) return vol.getpadvalue();
         else                       return _padvalue;
       }
       T& extrapval() const {
         return _extrapval;
       }
       bool xvalid(const volume<T>& vol) const {
-        if (_use_default_validity) return std::get<0>(vol.ep_valid);
+        if (_use_default_validity) return vol.getextrapolationvalidity()[0];
         else                       return _xvalid;
       }
       bool yvalid(const volume<T>& vol) const {
-        if (_use_default_validity) return std::get<1>(vol.ep_valid);
+        if (_use_default_validity) return vol.getextrapolationvalidity()[1];
         else                       return _yvalid;
       }
       bool zvalid(const volume<T>& vol) const {
-        if (_use_default_validity) return std::get<2>(vol.ep_valid);
+        if (_use_default_validity) return vol.getextrapolationvalidity()[2];
         else                       return _zvalid;
       }