OpenCV 2.3 Mat访问单通道矩阵元素

Question

这就是它应该如何做，如果我尝试简单的代码，它是有效的：

Mat a= Mat(4,3, CV_32FC1);
float elem_a= a.at<float>(i,j); 

但是，在做了一些数学运算之后，这段代码会给出工作结果

Mat intrinsics(3, 3, CV_32FC1 );  
Mat distortion( 5, 1, CV_32FC1 );
fs["camera_matrix"] >> intrinsics; //3*3
fs["distortion_coefficients"] >> distortion; //5*1

Mat rvec( 1, 3, CV_32FC1 );
Mat tvec( 1, 3, CV_32FC1 );
Mat R( 3, 3, CV_32FC1 );
Mat A( 3, 3, CV_32FC1 );

solvePnP( Mat(objectPoints), Mat(imagePoints), intrinsics, distortion, rvec, tvec, false );

Rodrigues( rvec, R );
A = intrinsics * R;

cout << "A = " << A << endl;
cout << "A[0] = " << A.at<float>(0,0) << "A[1] = " << A.at<float>(0,1) << endl;

输出：

A = 
 [-123.6820813196553, 792.0751394843999, -359.9404307669494;
  668.8426426360758, -15.08087511838299, -513.8498143647524;
  -0.3389607187919322, -0.03644067597638417, -0.9400945209128925]

A[0] = 4.12987e+09 A[1] = -3.48313

我做错了什么？Ty

Answer 1

请检查A矩阵的数据类型。我认为它被默默地转换成了CV_64F。