【OpenCv】Mat中常用的一些

//原文：http://blog.csdn.net/moc062066/article/details/6949894

//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 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;
 }

/****************************************在另一篇文章里看到的************************************、

说到数据的存储，这一直就是一个值得关注的问题，

Mat_<uchar>对应的是CV_8U

Mat_<char>对应的是CV_8S，

Mat_<int>对应的是CV_32S，

Mat_<float>对应的是CV_32F，

Mat_<double>对应的是CV_64F，

对应的数据深度如下：  

CV_8U - 8-bit unsigned integers ( 0..255 )  

 CV_8S - 8-bit signed integers ( -128..127 )  

 CV_16U - 16-bit unsigned integers ( 0..65535 )  

CV_16S - 16-bit signed integers ( -32768..32767 )  

CV_32S - 32-bit signed integers ( -2147483648..2147483647 ) 

CV_32F - 32-bit ?oating-point numbers ( -FLT_MAX..FLT_MAX, INF, NAN )  

CV_64F - 64-bit ?oating-point numbers ( -DBL_MAX..DBL_MAX, INF, NAN )  

这里还需要注意一个问题，很多OpenCV的函数支持的数据深度只有8位和32位的，所以要少使用CV_64F，但是vs的编译器又会把float数据自动变成double型，有些不太爽。