学步园

因为学习需要，所以要用到矩阵相乘，看别人的程序，会用到cvGEMM，但这是OpenCV的老函数了，网上都是老式的用法，新版的操作方法几乎没有说明，查了一下函数库，有gemm函数可以代替，描述如下：

Performs generalized matrix multiplication.
C++: void gemm(InputArray src1, InputArray src2, double alpha, InputArray src3, double gamma, OutputArray dst, int flags=0 )

src1 – first multiplied input matrix that should have CV_32FC1, CV_64FC1, CV_32FC2, orCV_64FC2 type.
src2 – second multiplied input matrix of the same type as src1.
alpha – weight of the matrix product.
src3 – third optional delta matrix added to the matrix product; it should have the same type
as src1 and src2.
beta – weight of src3.
dst – output matrix; it has the proper size and the same type as input matrices.
flags – operation flags:
– GEMM_1_T transposes src1.
– GEMM_2_T transposes src2.
– GEMM_3_T transposes src3

于是写了以下的语句：

 Mat   T;
 Mat   A=Mat::eye(1,3,CV_32FC1);
 Mat   C=Mat::eye(3,3,CV_32FC1);
 std::cout<<"A="<<A<<std::endl<<"C="<<C<<std::endl;
 gemm(A,C,1,0,1,T,0);
 std::cout<<"T="<<T;

编译没问题，但运行就悲剧了，不知名原因异常弹出！！后来试了又试，终于调通了：

 Mat   T;
 Mat   A=Mat::eye(1,3,CV_32FC1);
 Mat   C=Mat::eye(3,3,CV_32FC1);
 std::cout<<"A="<<A<<std::endl<<"C="<<C<<std::endl;
 gemm(A,C,1,10,0,T,0);//the src3 can't be 0,so if you 
			//want to ignore the src3,
                        //you should set the b  eater as 0
 std::cout<<"T="<<T;

如果你不想做加操作，也就是如果你想忽略src3时，不可以把src3设为0，而应该把beater设为0，这样src3就不会影响运算。