Rigid body 2-D image co-registration (translation and rotation) is performed using maximization of mutual information.
Function is implemented in c-code and compiled using the Matlab compiler to minimize computation time. Current compilation will only run on a 32-Bit windows machine running 2007b. Matlab compiler is necessary to re-compile for other versions/platforms.
Mutual information joint entropy matrix is computed using the Hanning windowed sinc function as the kernel of interpolation, which is the HPV estimation method .
Maximization of the joint entropy matrix is carried out using Powel's Direction set method  with original c-code very slightly modified from J.P. Moreau's code.
 Lu X, et al., Mutual information-based multimodal image registration using a novel joint histogram estimation, Comput Med Imaging Graph (2008), doi:10.1016/j.compmedimag.2007.12.001
 Numerical Recipes, The Art of Scientific Computing By W.H. Press, B.P. Flannery, S.A. Teukolsky and W.T. Vetterling, Cambridge University Press, 1986