仿射变换代码opencv

 //Rotation angle in degrees. 
 //Positive values mean counter-clockwise rotation
 //(thecoordinate origin is assumed to be the top-left corner).
	

cv::Mat cv::getRotationMatrix2D( Point2f center, double angle, double scale )
 	{
 	    CV_INSTRUMENT_REGION();
 	
 	    angle *= CV_PI/180;
 	    double alpha = std::cos(angle)*scale;
 	    double beta = std::sin(angle)*scale;
 	
 	    Mat M(2, 3, CV_64F);
 	    double* m = M.ptr();
 	//获取矩阵M的底层数据指针，用于直接访问矩阵元素。
 	    m[0] = alpha;
 	    m[1] = beta;
 	    m[2] = (1-alpha)*center.x - beta*center.y;
 	    m[3] = -beta;
 	    m[4] = alpha;
 	    m[5] = beta*center.x + (1-alpha)*center.y;
 	
 	    return M;
 	}

顺时针为正，左上角为默认坐标原点

CV_INSTRUMENT_REGION()是一个OpenCV宏，用于在代码中进行性能分析和测量。它可以用于标记代码的某个区域，以便在运行时获取该区域的性能指标。（不太明白，先放一下）