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<T,n>

typedef Vec<uchar, 2> Vec2b;
typedef Vec<uchar, 3> Vec3b;
typedef Vec<uchar, 4> Vec4b;

typedef Vec<short, 2> Vec2s;
typedef Vec<short, 3> Vec3s;
typedef Vec<short, 4> Vec4s;

typedef Vec<ushort, 2> Vec2w;
typedef Vec<ushort, 3> Vec3w;
typedef Vec<ushort, 4> Vec4w;    
    
typedef Vec<int, 2> Vec2i;
typedef Vec<int, 3> Vec3i;
typedef Vec<int, 4> Vec4i;
typedef Vec<int, 6> Vec6i;
typedef Vec<int, 8> Vec8i;

typedef Vec<float, 2> Vec2f;
typedef Vec<float, 3> Vec3f;
typedef Vec<float, 4> Vec4f;
typedef Vec<float, 6> Vec6f;

typedef Vec<double, 2> Vec2d;
typedef Vec<double, 3> Vec3d;
typedef Vec<double, 4> Vec4d;
typedef Vec<double, 6> 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 depthswitch ( 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 channelsswitch( 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;}