OpenCV中用于cv::Mat的自定义类型

Question

OpenCV中用于cv::Mat的自定义类型

3

我想使用自定义类型创建一个cv::Mat数组。以下是我的代码：

typedef struct{
  int x;
  int y;
  float prob;
}CellXY;

void main(){

  cv::Mat_<CellXY> map(10, 10);

  std::cout << "Width = " << map.cols << ", Height = " << map.rows << std::endl;
  std::cout << "### Assignment ###" << std::endl;
  for (int j=0; j<map.rows; j++){
    for (int i=0; i<map.cols; i++){
      map.at<CellXY>(j, i).x = i;
      map.at<CellXY>(j, i).y = j;
      map.at<CellXY>(j, i).prob = (float)(i + j * map.cols);

      std::cout << map.at<CellXY>(j, i).prob 
        << " (" << map.at<CellXY>(j, i).x
        << "," << map.at<CellXY>(j, i).y
        << ")\t";
    }
    std::cout << std::endl;
  }

  std::cout << "### Display ###" << std::endl;
  for (int j=0; j<map.rows; j++){
    for (int i=0; i<map.cols; i++){
      std::cout << map.at<CellXY>(j, i).prob 
        << " (" << map.at<CellXY>(j, i).x
        << "," << map.at<CellXY>(j, i).y
        << ")\t";
    }
    std::cout << std::endl; 
  }
  map.release();
}

然而，“任务”和“展示”部分之间的结果并不相同：

我应该如何使这些结果一致？

- puwanan

1个回答

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- Miki · Accepted Answer

这是因为OpenCV不知道您类的DataType。您需要为其进行专门化处理，例如：

typedef struct {
    int x;
    int y;
    float prob;
}CellXY;


// Add this!!!!!!
namespace cv {
template<> class DataType<CellXY>
{
public:
    typedef CellXY      value_type;
    typedef value_type  work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
        depth        = CV_32F, // Might cause problems... I'm saying it's all made of floats (and not 2 int a 1 float)
        channels     = 3,
        fmt          = (int)'p',
        type         = CV_MAKETYPE(depth, channels)
    };
};
}

void main() {
    ...
}

但总体而言，我认为最好避免与这些实现细节打交道，而只使用更好的数据结构。建议是：仅针对原始类型使用Mat。实际上，在其他OpenCV函数中也无法使用它...

以下是解决问题的几种方法：

Use another data structure: e.g. a std::vector<std::vector<CellXY>> or an "unrolled" std::vector<CellXY>

Make a class CellXYMatrix which deals with storing the CellXY:

class CellXYMatrix
{
     std::vector<CellXY> _mat; // your matrix of CellXY
     int _r; // rows
     int _c; // cols

public:
     CellXYMatrix(int rows, int cols) : _r(rows), _c(cols), _mat(rows * cols) {};

     void set(int row, int col, const CellXY& cell) {
        _mat[row * _c + col] = cell;
     }
     CellXY& get(int row, int col) {
        return _mat[row * _c + col];
     }  
}

You can eventually overload operator() to make the access similar to OpenCV Mats.

If the x and y fields in CellXY refer to the matrix position, why do you need them? You can simply have a Mat1f (aka Mat_<float>) for your probabilities, and x,y are the position in the matrix.