How is comma delimited initializer for OpenCV Mat implemented using C ++?
#include <iostream>
#include <opencv2/opencv.hpp>
using namespace std;
using namespace cv;
int main() {
Mat a = (Mat_<double>(3, 3) << 0, 1, 2, 3, 4, 5, 6, 7, 8);
cout << a << endl;
return 0;
}
How is comma delimited initializer for OpenCV Mat implemented with C ++?
How does "1" get into the matrix after "0"?
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1 answer
To allow initialization like
Mat a = (Mat_<double>(3, 3) << 0, 1, 2, 3, 4, 5, 6, 7, 8);
OpenCV first uses
template <typename T>
MatCommaInitializer_<T> operator<<(Mat_<T>&, T);
to return an intermediate object MatCommaInitializer_<T>
. This object has an overload operator,
, namely
template <typename T2>
MatCommaInitializer_<T>& operator,(T2 v);
which adds value to the initializer. Then there is a constructor
template <typename T>
explicit Mat(MatCommaInitializer_<T> const&);
to create an object Mat
from MatCommaInitializer
.
Note. You can find such information in the OpenCV documentation http://docs.opencv.org/master/ ( http://docs.opencv.org/master/d6/d9e/classcv_1_1MatCommaInitializer__.html ).
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