Examples of two-dimensional pointer-based encoding. The gray rectangles in the upper pictures indicate repeated regions that are encoded using pointers. In the particular scheme used here, each of these regions is required to contain at least 25 cells that have not already been encoded using pointers. The images are scanned sequentially and at every point the maximal rectangle extending to the right and down is found that is a repeat of a rectangle previously encountered, and contains the largest number of cells not already encoded using pointers. In many cases this maximal rectangle overlaps those found at subsequent points.