OpenCv学习笔记(一)----OpenCv中Mat类源码的详细解读(2)

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(一)像素存储的方法

    1--本节我们讲解如何存储像素,存储像素值,需要指定:
        1--颜色空间
        2--数据类型
    2--其中,颜色空间是指针对一个给定的颜色,如何组合颜色以其编码。
    3--最简单的颜色空间是----灰度级空间----只需要处理：黑色和白色,对它们进行组合便可以产生不同程度的灰
       色(256灰度级)
    4--对于彩色方式---则有更多种类的颜色空间,但不论那种方式,都是把颜色分成:三个或者四个---基元素,通过
       组合基元素,就可以产生所有的颜色
       1--RGB颜色空间是最常用的一种颜色空间,这归功于它也是人眼内部构成颜色的方式,它的基色是--红色,绿色
          蓝色,有时为了表示透明颜色,也会加入第四个元素alpha(A)
       2--彩色转灰度的公式:
                        Gray = R*0.299 + G*0.587 + B*0.114
    5--颜色系统有很多,它们各有优势:
       1--RGB是最常见的,这是因为人眼采用了相似的工作机制,它被显示设备所采用
       2--HSV和HLS把颜色分解为--色调,饱和度,亮度和明度，这是描述颜色最自然的方式

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（二）具体像素在内存空间中的存储—很重要的一个知识点

       1--每个组成元素都有自己的定义域,而定义域的大小取决于其数据类型,如何存储一个元素决定了我们在其定义
          域上能够控制的---精度
       2--最小的数据类型是---char,占一个字节8位,可以使有符号型(-127--127)，也可以是无符号型(0--255)
       3--尽管使用三个char型已经可以表示1600万种坑的颜色(RGB)颜色空间,但是若使用float(4字节32位)或者
          double(8字节64位),则能够更加精细的描述颜色分辨率的能力。但是，同时，图片所占用的存储空间也会
          成倍的增加

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（三）Mat类–OpenCv中Mat类源代码的阅读

 1--源代码的具体位置位于---core.hpp文件中:
 2--比如说我的OpenCv安装在C盘中,那么它所对应的目录就是:
    C:\Program Files\opencv\build\include\opencv2\core

/*********************************************************************************************
程序功能:
        OpenCv2.4.8之Mat类--OpenCv源代码解读
        OpenCv2.4.8+VS2010
地点时间:
        陕西师范大学 2016.4.21
作者信息:
        九月
**********************************************************************************************/
//【1】这是OpenCv源代码中,Mat类的定义部分
//【2】CV_EXPORTS--这个修饰符,我们先不探究它是什么
//【3】我们先重点看一下Mat都有哪些:
      1--构造函数
      2--成员方法(或者说成员函数)
      3--数据成员
 //【4】class Mat{}；----标准的C++类定义，大家在这块注意一下,C++中类定义完成的最后有一个分号";"，
      在java语言中,类的定义是没有的,而且C++中类的定义没有用public修饰,而C++默认的修饰符是private,
      结构体默认的修饰符是public(这也是C++中结构体与类类型的最主要的区别)
 //【5】Mat类的--声明 
class CV_EXPORTS Mat
{
public:
    //! default constructor
    //【1】Mat类默认的构造函数
    Mat();
    //! constructs 2D matrix of the specified size and type
    // (_type is CV_8UC1, CV_64FC3, CV_32SC(12) etc.)
    //【2】通过指定一个矩阵的rows行和cols列以及类型，来构造一个指定大小的2维矩阵
    Mat(int rows, int cols, int type);
    //【3】和上面的一样,这里只不过是把二维矩阵的rows行和cols列封装在一个Size这样的类,用它来指定一个大小的
          确定的二维矩阵(确定宽和高的图像)
    //【4】这里的Size其实是一个类模板,具体是什么,大家可以去分析源代码
    Mat(Size size, int type);
    //! constucts 2D matrix and fills it with the specified value _s.
    //【5】构造一个指定大小和类型的Mat对象,并且用指定的Scalar颜色去填充它
    Mat(int rows, int cols, int type, const Scalar& s);
    Mat(Size size, int type, const Scalar& s);
    //【6】构造一个N维的矩阵
    //! constructs n-dimensional matrix
    Mat(int ndims, const int* sizes, int type);
    Mat(int ndims, const int* sizes, int type, const Scalar& s);
    //! copy constructor
    //【7】C++中的复制构造函数---特点:只有单个形参,而且该形参是对本类类型对象的应用常量,这类构造函数称为--
          复制构造函数
    //【8】此块Mat类重载了一个Mat的复制构造函数
    Mat(const Mat& m);
    //! constructor for matrix headers pointing to user-allocated data
    //【9】构造一个指定大小和类型的Mat信息头,并且指向用户已经分配的数据
    Mat(int rows, int cols, int type, void* data, size_t step=AUTO_STEP);
    Mat(Size size, int type, void* data, size_t step=AUTO_STEP);
    Mat(int ndims, const int* sizes, int type, void* data, const size_t* steps=0);

    //! creates a matrix header for a part of the bigger matrix
    //【10】构造一个大矩阵一部分的信息头
    Mat(const Mat& m, const Range& rowRange, const Range& colRange=Range::all());
    Mat(const Mat& m, const Rect& roi);
    Mat(const Mat& m, const Range* ranges);
    //! converts old-style CvMat to the new matrix; the data is not copied by default
    //【11】这个构造函数用于老式的cvMat矩阵和Mat类对象的转换
    Mat(const CvMat* m, bool copyData=false);
    //! converts old-style CvMatND to the new matrix; the data is not copied by default
    Mat(const CvMatND* m, bool copyData=false);
    //! converts old-style IplImage to the new matrix; the data is not copied by default
    Mat(const IplImage* img, bool copyData=false);
    //! builds matrix from std::vector with or without copying the data
    template<typename _Tp> explicit Mat(const vector<_Tp>& vec, bool copyData=false);
    //! builds matrix from cv::Vec; the data is copied by default
    template<typename _Tp, int n> explicit Mat(const Vec<_Tp, n>& vec, bool copyData=true);
    //! builds matrix from cv::Matx; the data is copied by default
    template<typename _Tp, int m, int n> explicit Mat(const Matx<_Tp, m, n>& mtx, bool copyData=true);
    //! builds matrix from a 2D point
    template<typename _Tp> explicit Mat(const Point_<_Tp>& pt, bool copyData=true);
    //! builds matrix from a 3D point
    template<typename _Tp> explicit Mat(const Point3_<_Tp>& pt, bool copyData=true);
    //! builds matrix from comma initializer
    template<typename _Tp> explicit Mat(const MatCommaInitializer_<_Tp>& commaInitializer);

    //! download data from GpuMat
    explicit Mat(const gpu::GpuMat& m);
    //【12】C++类中很重要的一个部分---析构函数
    //! destructor - calls release()

    ~Mat();
    //! assignment operators
    //【13】Mat类中的运算符重载
    Mat& operator = (const Mat& m);
    Mat& operator = (const MatExpr& expr);

    //! returns a new matrix header for the specified row
    Mat row(int y) const;
    //! returns a new matrix header for the specified column
    Mat col(int x) const;
    //! ... for the specified row span
    Mat rowRange(int startrow, int endrow) const;
    Mat rowRange(const Range& r) const;
    //! ... for the specified column span
    Mat colRange(int startcol, int endcol) const;
    Mat colRange(const Range& r) const;
    //! ... for the specified diagonal
    // (d=0 - the main diagonal,
    //  >0 - a diagonal from the lower half,
    //  <0 - a diagonal from the upper half)
    Mat diag(int d=0) const;
    //! constructs a square diagonal matrix which main diagonal is vector "d"
    static Mat diag(const Mat& d);

    //! returns deep copy of the matrix, i.e. the data is copied
    //【14】Mat类中的---深复制----的一个函数
    //【15】Mat A=B.clone()--将对象B的信息头，矩阵指针以及矩阵体全部复制给对象A
    Mat clone() const;
    //! copies the matrix content to "m".
    // It calls m.create(this->size(), this->type()).
    //【16】也是深复制B.copyTo(A),作用同Mat A=B.clone()
    void copyTo( OutputArray m ) const;
    //! copies those matrix elements to "m" that are marked with non-zero mask elements.
    void copyTo( OutputArray m, InputArray mask ) const;
    //! converts matrix to another datatype with optional scalng. See cvConvertScale.
    void convertTo( OutputArray m, int rtype, double alpha=1, double beta=0 ) const;

    void assignTo( Mat& m, int type=-1 ) const;

    //! sets every matrix element to s
    //【17】将图片中(矩阵)的每一个像素颜色设置为颜色s
    Mat& operator = (const Scalar& s);
    //! sets some of the matrix elements to s, according to the mask
    //【18】根据掩膜设置图片的颜色
    Mat& setTo(InputArray value, InputArray mask=noArray());
    //! creates alternative matrix header for the same data, with different
    // number of channels and/or different number of rows. see cvReshape.
    Mat reshape(int cn, int rows=0) const;
    Mat reshape(int cn, int newndims, const int* newsz) const;

    //! matrix transposition by means of matrix expressions
    MatExpr t() const;
    //! matrix inversion by means of matrix expressions
    MatExpr inv(int method=DECOMP_LU) const;
    //! per-element matrix multiplication by means of matrix expressions
    MatExpr mul(InputArray m, double scale=1) const;

    //! computes cross-product of 2 3D vectors
    Mat cross(InputArray m) const;
    //! computes dot-product
    double dot(InputArray m) const;

    //! Matlab-style matrix initialization
    //【19】Matlab风格的矩阵初始化函数，指定矩阵的大小和类型
    static MatExpr zeros(int rows, int cols, int type);
    static MatExpr zeros(Size size, int type);
    static MatExpr zeros(int ndims, const int* sz, int type);
    static MatExpr ones(int rows, int cols, int type);
    static MatExpr ones(Size size, int type);
    static MatExpr ones(int ndims, const int* sz, int type);
    static MatExpr eye(int rows, int cols, int type);
    static MatExpr eye(Size size, int type);

    //! allocates new matrix data unless the matrix already has specified size and type.
    // previous data is unreferenced if needed.
    void create(int rows, int cols, int type);
    void create(Size size, int type);
    void create(int ndims, const int* sizes, int type);

    //! increases the reference counter; use with care to avoid memleaks
    void addref();
    //! decreases reference counter;
    // deallocates the data when reference counter reaches 0.
    void release();

    //! deallocates the matrix data
    void deallocate();
    //! internal use function; properly re-allocates _size, _step arrays
    void copySize(const Mat& m);

    //! reserves enough space to fit sz hyper-planes
    void reserve(size_t sz);
    //! resizes matrix to the specified number of hyper-planes
    void resize(size_t sz);
    //! resizes matrix to the specified number of hyper-planes; initializes the newly added elements
    void resize(size_t sz, const Scalar& s);
    //! internal function
    void push_back_(const void* elem);
    //! adds element to the end of 1d matrix (or possibly multiple elements when _Tp=Mat)
    template<typename _Tp> void push_back(const _Tp& elem);
    template<typename _Tp> void push_back(const Mat_<_Tp>& elem);
    void push_back(const Mat& m);
    //! removes several hyper-planes from bottom of the matrix
    void pop_back(size_t nelems=1);

    //! locates matrix header within a parent matrix. See below
    void locateROI( Size& wholeSize, Point& ofs ) const;
    //! moves/resizes the current matrix ROI inside the parent matrix.
    Mat& adjustROI( int dtop, int dbottom, int dleft, int dright );
    //! extracts a rectangular sub-matrix
    // (this is a generalized form of row, rowRange etc.)
    Mat operator()( Range rowRange, Range colRange ) const;
    Mat operator()( const Rect& roi ) const;
    Mat operator()( const Range* ranges ) const;

    //! converts header to CvMat; no data is copied
    operator CvMat() const;
    //! converts header to CvMatND; no data is copied
    operator CvMatND() const;
    //! converts header to IplImage; no data is copied
    operator IplImage() const;

    template<typename _Tp> operator vector<_Tp>() const;
    template<typename _Tp, int n> operator Vec<_Tp, n>() const;
    template<typename _Tp, int m, int n> operator Matx<_Tp, m, n>() const;

    //! returns true iff the matrix data is continuous
    // (i.e. when there are no gaps between successive rows).
    // similar to CV_IS_MAT_CONT(cvmat->type)
    bool isContinuous() const;

    //! returns true if the matrix is a submatrix of another matrix
    bool isSubmatrix() const;

    //! returns element size in bytes,
    // similar to CV_ELEM_SIZE(cvmat->type)
    //【21】返回图像中每一个像素元素的大小
    size_t elemSize() const;
    //! returns the size of element channel in bytes.
    size_t elemSize1() const;
    //! returns element type, similar to CV_MAT_TYPE(cvmat->type)
    //【22】返回元素的类型
    int type() const;
    //! returns element type, similar to CV_MAT_DEPTH(cvmat->type)
    int depth() const;
    //! returns element type, similar to CV_MAT_CN(cvmat->type)
    int channels() const;
    //! returns step/elemSize1()
    size_t step1(int i=0) const;
    //! returns true if matrix data is NULL
    bool empty() const;
    //! returns the total number of matrix elements
    //【23】返回整幅图片中元素的---像素点的---总数
    //【24】一幅图片中像素点的总数=图片的高度*图片的宽度=rows*cols
    size_t total() const;

    //! returns N if the matrix is 1-channel (N x ptdim) or ptdim-channel (1 x N) or (N x 1); negative number otherwise
    int checkVector(int elemChannels, int depth=-1, bool requireContinuous=true) const;

    //! returns pointer to i0-th submatrix along the dimension #0
    //【25】这几个函数用在----变量图像中的每一个像素的时候
    //【26】用于操作一副图片中的每一个像素
    //【27】后面将会用一节具体的讲解
    uchar* ptr(int i0=0);
    const uchar* ptr(int i0=0) const;

    //! returns pointer to (i0,i1) submatrix along the dimensions #0 and #1
    uchar* ptr(int i0, int i1);
    const uchar* ptr(int i0, int i1) const;

    //! returns pointer to (i0,i1,i3) submatrix along the dimensions #0, #1, #2
    uchar* ptr(int i0, int i1, int i2);
    const uchar* ptr(int i0, int i1, int i2) const;

    //! returns pointer to the matrix element
    uchar* ptr(const int* idx);
    //! returns read-only pointer to the matrix element
    const uchar* ptr(const int* idx) const;

    template<int n> uchar* ptr(const Vec<int, n>& idx);
    template<int n> const uchar* ptr(const Vec<int, n>& idx) const;

    //! template version of the above method
    template<typename _Tp> _Tp* ptr(int i0=0);
    template<typename _Tp> const _Tp* ptr(int i0=0) const;

    template<typename _Tp> _Tp* ptr(int i0, int i1);
    template<typename _Tp> const _Tp* ptr(int i0, int i1) const;

    template<typename _Tp> _Tp* ptr(int i0, int i1, int i2);
    template<typename _Tp> const _Tp* ptr(int i0, int i1, int i2) const;

    template<typename _Tp> _Tp* ptr(const int* idx);
    template<typename _Tp> const _Tp* ptr(const int* idx) const;

    template<typename _Tp, int n> _Tp* ptr(const Vec<int, n>& idx);
    template<typename _Tp, int n> const _Tp* ptr(const Vec<int, n>& idx) const;

    //! the same as above, with the pointer dereferencing
    template<typename _Tp> _Tp& at(int i0=0);
    template<typename _Tp> const _Tp& at(int i0=0) const;

    template<typename _Tp> _Tp& at(int i0, int i1);
    template<typename _Tp> const _Tp& at(int i0, int i1) const;

    template<typename _Tp> _Tp& at(int i0, int i1, int i2);
    template<typename _Tp> const _Tp& at(int i0, int i1, int i2) const;

    template<typename _Tp> _Tp& at(const int* idx);
    template<typename _Tp> const _Tp& at(const int* idx) const;

    template<typename _Tp, int n> _Tp& at(const Vec<int, n>& idx);
    template<typename _Tp, int n> const _Tp& at(const Vec<int, n>& idx) const;

    //! special versions for 2D arrays (especially convenient for referencing image pixels)
    template<typename _Tp> _Tp& at(Point pt);
    template<typename _Tp> const _Tp& at(Point pt) const;

    //! template methods for iteration over matrix elements.
    // the iterators take care of skipping gaps in the end of rows (if any)
    template<typename _Tp> MatIterator_<_Tp> begin();
    template<typename _Tp> MatIterator_<_Tp> end();
    template<typename _Tp> MatConstIterator_<_Tp> begin() const;
    template<typename _Tp> MatConstIterator_<_Tp> end() const;

    enum { MAGIC_VAL=0x42FF0000, AUTO_STEP=0, CONTINUOUS_FLAG=CV_MAT_CONT_FLAG, SUBMATRIX_FLAG=CV_SUBMAT_FLAG };

    /*! includes several bit-fields:
         - the magic signature
         - continuity flag
         - depth
         - number of channels
     */
    int flags;
    //! the matrix dimensionality, >= 2
    //【28】这是Mat类的数据成员--------第四部分重要的内容----数据成员----成员属性
    //【29】用于记录矩阵(图片)的维数
    int dims;
    //! the number of rows and columns or (-1, -1) when the matrix has more than 2 dimensions
    //【30】用于记录矩阵的rows行和cols列
    //【31】rows---nHeight----图形的高度
    //【32】cols---nWidth-----图像的宽度
    int rows, cols;
    //! pointer to the data
    uchar* data;

    //! pointer to the reference counter;
    // when matrix points to user-allocated data, the pointer is NULL
    int* refcount;

    //! helper fields used in locateROI and adjustROI
    uchar* datastart;
    uchar* dataend;
    uchar* datalimit;

    //! custom allocator
    MatAllocator* allocator;

    struct CV_EXPORTS MSize
    {
        MSize(int* _p);
        Size operator()() const;
        const int& operator[](int i) const;
        int& operator[](int i);
        operator const int*() const;
        bool operator == (const MSize& sz) const;
        bool operator != (const MSize& sz) const;

        int* p;
    };

    struct CV_EXPORTS MStep
    {
        MStep();
        MStep(size_t s);
        const size_t& operator[](int i) const;
        size_t& operator[](int i);
        operator size_t() const;
        MStep& operator = (size_t s);

        size_t* p;
        size_t buf[2];
    protected:
        MStep& operator = (const MStep&);
    };
    //【33】一行含有的字节数
    MSize size;
    MStep step;

protected:
    void initEmpty();
};

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