移动语义和 cv::Mat

Question

Opencv's documentation on cv::Mat 似乎表明目前没有移动构造函数，所以像 cv::Mat A=std::move(some_other_cv_mat) 这样的东西没有多大意义。我目前（和天真的）解决这个问题的方法是从 cv::Mat 派生一个 class，为此我实现了一个移动构造函数，如下所示：

namespace cv
{
    //matrix object derived from cv::Mat
    class Mvbl_Mat final: public Mat 
    {
        public:
          //constructors
          Mvbl_Mat(){};
          Mvbl_Mat(int rows, int cols, int type, const Scalar   &s):Mat(rows, cols, type, s){}
         //destructor
         ~Mvbl_Mat(){};

          //move constructor
          Mvbl_Mat(Mvbl_Mat && other) noexcept
          {   
              this->data=other.data;
              other.data=nullptr;
           } 
          //move assignment operator
          Mvbl_Mat & operator=(Mvbl_Mat && other)
          {   
              this->data=other.data;
              other.data=nullptr;
              return *this; 
          }   
     };

}

虽然这适用于我目前面临的有限问题，但显然存在很多限制，而且解决方案远非理想。那么，模拟 cv::Mat 移动语义的最佳方法是什么？

Answer 1

没有必要这样做。 cv::Mat 的复制构造函数实际上并没有复制数据。它基本上是一个引用，所有对象共享相同的数据。

cv::Mat::Mat(const Mat & m)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

m Array that (as a whole or partly) is assigned to the constructed matrix. No data is copied by these constructors. Instead, the header pointing to m data or its sub-array is constructed and associated with it. The reference counter, if any, is incremented. So, when you modify the matrix formed using such a constructor, you also modify the corresponding elements of m . If you want to have an independent copy of the sub-array, use Mat::clone()

Answer 2

截至 4.x OpenCV 提供 Mat (Mat &&m) and Mat & operator= (Mat &&m)。

如果您使用的是 4.x 之前的版本，我建议您查看 cv::Mat 中定义的移动构造函数和移动赋值运算符实现，modules/core/include/opencv2/core/mat.inl.hpp，因为它比复制 .data 成员要复杂一些。

移动语义和 cv::Mat

move semantics and cv::Mat

c++

opencv

computer-vision

move-semantics

c++11