MATLAB Implementation of Nonrigid Registration Using Free-Form Deformation

This MATLAB source code implements nonrigid registration using Free-Form Deformation methodology. This approach is particularly valuable in medical image processing and computer vision domains, as it enables precise alignment of non-rigidly deformed objects. The method achieves deformation by manipulating control points on a B-spline grid to warp the object's surface geometry, resulting in significantly improved registration accuracy. The implementation incorporates sophisticated algorithms including B-spline interpolation, gradient-based optimization techniques, and multi-resolution registration strategies to ensure robust and reliable alignment results. The code structure features modular functions for grid initialization, deformation field computation, similarity metric evaluation (such as mutual information or sum of squared differences), and optimization loop management. Comprehensive inline comments and documentation are provided throughout the codebase to facilitate understanding of the implementation logic, parameter tuning guidelines, and algorithmic workflows. Key functions include FFD grid manipulation, coordinate transformation routines, and optimization handlers that collectively enable flexible deformation control. Researchers interested in nonrigid registration methodologies are strongly encouraged to utilize this code for experimental validation and further development.