对于一幅图像，很多时候我们感兴趣的是图像中的某部分，同时有时候要对目标进行跟踪时，需要选取目标特征，所以要提取图像的感兴趣区域。使用cvsetImageROI函数-For an image, many times we are interested in a certain part of the image, sometimes at the same time to the target track, you need to　the target feature, so you want to extract the region of interest of the image. Use cvsetImageROI function