void Test_ROIWith2Image()
{
Mat g_srcImage=imread("D:\\OpenCV Projects\\OpenCV_Test_Image\\6.jpg");
Mat g_srcImagelogo=imread("D:\\OpenCV Projects\\OpenCV_Test_Image\\logo1.jpg");
//在原图上创建一个ROI区域(left,top,width,height)
Mat g_roiImage=g_srcImage(Rect(100,50,g_srcImagelogo.cols,g_srcImagelogo.rows));
//以灰度存储图像
Mat g_mask=imread("D:\\OpenCV Projects\\OpenCV_Test_Image\\logo1.jpg",0);
//将mask合并到ROI区域
g_srcImagelogo.copyTo(g_roiImage,g_mask);
imshow("原图",g_srcImage);
imshow("ROI原图",g_srcImagelogo);
}

原文:http://www.cnblogs.com/foggia2004/p/6596752.html