public:
virtual int NumFrames() const = 0;
virtual int Col(int frame) const = 0;
virtual int Row(int frame) const = 0;
virtual geometry::Vector<int> Offset(int frame) const { return geometry::Vector<int>(); }
public:
virtual int NumFrames() const = 0;
virtual int Col(int frame) const = 0;
virtual int Row(int frame) const = 0;
virtual geometry::Vector<int> Offset(int frame) const { return geometry::Vector<int>(); }