c++ - OpenCV: How to Efficiently Multiply Each Element of a Mat2d matrix by a Mat1d matrix -

i have mat2d matrix, each element 2d vector. example:

[[x0, y0], [x1, y1]  [x2, y2], [x3, y3]] 

i want left multiply each of these vectors mat1d camera matrix:

[fx, 0,  cx,   0,  fy, cy,   0,  0,  1] 

(each vector represents location of vertex in grid want convert camera space pixel space.)

the resulting matrix, example, be:

[[x0 * fx + cx, y0 * fy + cy], [x1 * fx + cx, y1 * fy + cy]  [x2 * fx + cx, y2 * fy + cy], [x3 * fx + cx, y3 * fy + cy]] 

what straightforward , efficient way accomplish this?

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here current approach:

mat2d points = getmesh(); mat1d cameramtrx = getcameramtrx();  for(int col = 0; col < points.cols; col++){     for(int row = 0; row < points.rows; row++){         points.at<vec2d>(row, col).val[0] = points.at<vec2d>(row, col)[0] * cameramtrx.at<double>(0, 0) + cameramtrx.at<double>(0, 2);         points.at<vec2d>(row, col).val[1] = points.at<vec2d>(row, col)[1] * cameramtrx.at<double>(1, 1) + cameramtrx.at<double>(1, 2);     } } 

opencv documentation has detailed various methods of iterating cv::mat efficiently, out of presented methods, efficient way use cv::lut(), context of question, guess range of input matrix values not fixed, look-up table can't created, helpful in case of rgb images, because know beforehand min value 0 , max value 255, can create lookup table, in problem, need multiply 2 matrices assume not images go the efficient way.

int cameramatrix[] = {2, 0, 10, 0, 4, 20, 0, 0, 1}; cv::mat mat(2, 2, cv_32fc2, cv::scalar(100, 20)); cv::size contsize = mat.size();  // calculate length of array if input matrix flatten, in case of continuous matrix only. if (mat.iscontinuous()) {     contsize.width *= contsize.height;     contsize.height = 1; }  cv::vec2f* ptr; (int = 0; < contsize.height; ++i) {     ptr = mat.ptr<cv::vec2f>(i);     (int j = 0; j < contsize.width; ++j)     {         ptr[j] = cv::vec2f(ptr[j].val[0]*cameramatrix[0] + cameramatrix[2], ptr[j].val[1] * cameramatrix[4] + cameramatrix[5]);     } }