正zigzag扫描和它的恢复。zigzag.m是zigzag扫描的程序，invzigzag.m是把扫描的值转换成原矩阵。-Positive zigzag scanning, and its restoration. zigzag.m the zigzag scanning process, invzigzag.m the scanned values ​ ​ are converted to the original matrix.