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POhow to initialize a Eigen Matrix from an opencv cv::Mat, or from an array which is row-major?
 

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    <p>I found that Eigen's Matrix is default column-major, which is like MATLAB, but how do I initialize an Eigen::MatrixXd from an cv::Mat? The following code is my test. But none of them could be compiled successfully. Could someone give me some advice, please? or some other links? Thanks.</p> <pre><code> cv::Mat A_M=cv::Mat(rows, cols, CV_64FC1); double *A=(double *)A_M.data(); typedef Map&lt;MatrixXd&gt; MapMat; MapMat A_eigen(A,m,n); Eigen::Matrix&lt;double,Eigen::Dynamic,Eigen::Dynamic,Eigen::RowMajor&gt; A_eigen; Eigen::Map&lt;Matrix&lt;double,Eigen::Dynamic,Eigen::Dynamic,Eigen::RowMajor&gt; &gt;(A,m,n) = A_eigen; </code></pre> <p>Updated:</p> <pre><code> double *A=(double *)A_M.data();//m*n double *B=(double *)B_M.data();//n*p double *C=(double *)C_M.data();//m*p //regular Eigen Matrix Eigen::MatrixXd A_eigenMat; Eigen::MatrixXd B_eigenMat; Eigen::MatrixXd C_eigenMat; Eigen::Map&lt;Eigen::Matrix&lt;double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor&gt; &gt; A_mappedMat (A, m, n); Eigen::Map&lt;Eigen::Matrix&lt;double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor&gt; &gt; B_mappedMat (B, n, p); Eigen::Map&lt;Eigen::Matrix&lt;double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor&gt; &gt; C_mappedMat (C, m, p); // Eigen handles the conversion from row major to column major A_eigenMat = A_mappedMat; B_eigenMat = B_mappedMat; C_eigenMat = C_mappedMat; // multiplication C_eigenMat=A_eigenMat*B_eigenMat; </code></pre> <p>Then, when I output the M_C, its result is wrong. It seems the C_eigenMat didn't copy the data into M_C.data.</p>
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