Template function implicit/explicit parameter

I am trying to use template function to do interpolation for pixel values.

I have two classes of interpolators that implements the interpolation algorithm.

class LinearInterpolator;
class NearestNeighborInterpolator;

I have different classes of images;

class ColorImage;
class GrayScaleImage;

I then have a function that does interpolation utilizing the specific interpolator you pick.

template<typename InterpType, typename ImageType, typename PelType> 
  bool getValue(const ImageType& image, PelPosition pos, PelType* pelValue);

In my calling code I have

getValue<LinearInterpolator>(ima开发者_如何学运维ge, pos, pelValue);

And I get the compiler error "missing template argument list". My question is: is what I am trying to do completely infeasible or am I missing something here.

---

All right. The full class declaration for LinearInterpolator actually looks like this...

template <
  typename ImageType, 
  typename OutputPixelType = typename ImageType::Pixel, 
  typename FieldType = double, 
  template<typename From, typename To, typename Enable = void> class OutputPixelConverter = StaticCast
>
class LinearInterpolator : public AbstractInterpolator;

So I ended up taking the InterpType out of the type parameter list and passing in an enum as the parameter...

Old >>>>>

template<typename InterpType, typename ImageType, typename PelType> 
  bool getValue(const ImageType& image, PelPosition pos, PelType* pelValue);

New >>>>>

template<typename ImageType, typename PelType> 
  bool getValue(InterpType interp, const ImageType& image, PelPosition pos, PelType* pelValue);

If there is a better way of doing it, please comment.