Mutual Information in 3D Image Registration with Boundary Handling

This program implements a mutual information algorithm for three-dimensional image registration. Beyond standard functionality, we have integrated sophisticated boundary handling mechanisms. This enhancement enables superior management of edge cases during the registration process, significantly improving both accuracy and stability. The implementation utilizes histogram-based probability distribution estimation and incorporates gradient-based optimization methods for efficient parameter search. Key features include: - Joint histogram calculation with normalized mutual information metric - Multi-resolution registration approach for computational efficiency - Boundary-aware interpolation techniques preventing invalid pixel references - Optimized gradient computation using finite differences - Adaptive step size control in optimization loop The boundary processing module specifically handles edge regions by implementing mirror padding and conditional interpolation, ensuring that transformation operations don't access out-of-bounds voxels while maintaining smooth intensity transitions.