中文说明：这是第一个步骤，以检测forsgery图像中的代码。分级工序是通过比较像素之间的关系Cyclobutyl实现，并找到相应的阈值。
English Description：
This is code for first step to detect forsgery in an image. The classification step is implemented by comparing the ralation between pixels and find the correspondant threshold.