Fig. 11

Sample hierarchical division process. In this example, it has been assumed that σ _max = 10, \(N_{itr}^{Tot}~=~4\), and the size of the frame is 16 × 16. For simplicity, the ROI range is defined less than σ _max . In the beginning, the entire frame is considered as one block. Since its metric value is greater than the metric value, it is divided into four blocks, and this process is continued until the number of iterations equals to \(N_{itr}^{Tot}\) or the metric values of all blocks are in the ROI range