cv::Mat经常用到的信息

//cv::Mat中获取图像中某一点的值是比较麻烦的，一一来探秘

//预备知识
/*
  /*\typedef
access individual elements using [] operator etc.
Shorter aliases for the most popular specializations of Vec

typedef Vec Vec2b;
typedef Vec Vec3b;
typedef Vec Vec4b;

typedef Vec Vec2s;
typedef Vec Vec3s;
typedef Vec Vec4s;

typedef Vec Vec2w;
typedef Vec Vec3w;
typedef Vec Vec4w;    
    
typedef Vec Vec2i;
typedef Vec Vec3i;
typedef Vec Vec4i;
typedef Vec Vec6i;
typedef Vec Vec8i;

typedef Vec Vec2f;
typedef Vec Vec3f;
typedef Vec Vec4f;
typedef Vec Vec6f;

typedef Vec Vec2d;
typedef Vec Vec3d;
typedef Vec Vec4d;
typedef Vec Vec6d;

----------------------imread，第二个参数------------------------
    enum
    {
        // 8bit, color or not
        IMREAD_UNCHANGED  =-1,
        // 8bit, gray
        IMREAD_GRAYSCALE  =0,
        // ?, color
        IMREAD_COLOR      =1,//默认
        // any depth, ?
        IMREAD_ANYDEPTH   =2,
        // ?, any color
        IMREAD_ANYCOLOR   =4
    };

------------------------Mat 常用信息------------------------------
    //! returns element type, similar to CV_MAT_TYPE(cvmat->type)

    int type() const;    //0，1，2，。。。，6

    //! returns element type, similar to CV_MAT_DEPTH(cvmat->type)

    int depth() const;

    常见的有：

      CV_8U   :
     CV_8S   :
     CV_16U  :
     CV_16S  :
     CV_32S  :
     CV_32F  :
     CV_64F  :

    
    //! returns element type, similar to CV_MAT_CN(cvmat->type)
    int channels() const; //1，2，3
    
    //! the matrix dimensionality, >= 2
    int dims;

    //! the number of rows and columns or (-1, -1) when the matrix has more than 2 dimensions
    int rows, cols;
    
    //! pointer to the data
    uchar* data;

------------------------------------
#define CV_8U   0
#define CV_8S   1
#define CV_16U  2
#define CV_16S  3
#define CV_32S  4
#define CV_32F  5
#define CV_64F  6
#define CV_USRTYPE1 7

CV_[The number of bits per item][Signed or Unsigned][Type Prefix]C[The channel number]

string show_Mat_type( Mat mat_input ){
	
	string mat_type_name = "";
	
	//detect depth
	switch ( mat_input.depth() ) {
	case CV_8U   :
			mat_type_name = "CV_8U";
			break;

	case CV_8S   :
			mat_type_name = "CV_8S";
			break;

	case CV_16U  :
			mat_type_name = "CV_16U";
			break;

	case CV_16S  :
			mat_type_name = "CV_16S";
			break;

	case CV_32S  :
			mat_type_name = "CV_32S";
			break;

	case CV_32F  :
			mat_type_name = "CV_32F";
			break;

	case CV_64F  :
			mat_type_name = "CV_64F";
			break;
			
	default:
		cout << "switch ( mat_input.depth() ) error!" << endl ;
	}
	
	//detect channels
	switch( mat_input.channels() ) {
	case 1 :
		mat_type_name += "C1";
		break;
		
	case 2 :
		mat_type_name += "C2";
		break;
		
	case 3 :
		mat_type_name += "C3";
		break;
		
	default:
		cout << "switch( mat_input.channels() ) error!" << endl ;
	}
	
	//uchar char short
    switch( mat_input.type() % 8 ) {
    case 0:
      //cout<<  int( ((uchar*)mat.data + Cols*i+Chns*j )[k] )<<" ";
      mat_type_name += " uchar";
      break;
      
    case 1:
      //cout<<  int( (  (char*)mat.data + Cols*i+Chns*j)[k] )<<" ";   
        mat_type_name += " char";
      break;
      
    case 2:
      //cout<<  (  (unsigned short*)mat.data + Cols*i+Chns*j)[k] <<" ";
        mat_type_name += " ushort";
      break;
      
    case 3:
      //cout<<  (  (short*)mat.data + Cols*i+Chns*j)[k] <<" ";   
        mat_type_name += " short";
      break;
      
    case 4:
      //cout<<  (  (int*)mat.data + Cols*i+Chns*j)[k] <<" ";   
        mat_type_name += " int";
      break;
      
    case 5:
      //cout<<  (  (float*)mat.data + Cols*i+Chns*j)[k] <<" ";
        mat_type_name += " float";
      break;
      
    case 6:
      //cout<<  (  (double*)mat.data + Cols*i+Chns*j)[k] <<" ";
        mat_type_name += " double";
      break;
      
    default:
       break;
    }
	cout << "\n" << mat_type_name << endl ;
	return mat_type_name;
}