网上查了很多，发现查资料不如查源码

以Cv为开头的类，都是不含有具体数据的（仅仅存储指针）

CvMat

typedef struct CvMat
{
    int type;
    int step;

    /* for internal use only */
    int* refcount;
    int hdr_refcount;

    union
    {
        uchar* ptr;
        short* s;
        int* i;
        float* fl;
        double* db;
    } data;
#ifdef __cplusplus union { int rows; int height; }; union { int cols; int width; };#else int rows; int cols;#endif}CvMat;


CV_INLINE CvMat cvMat( int rows, int cols, int type, void* data CV_DEFAULT(NULL))
{
    CvMat m;

    assert( (unsigned)CV_MAT_DEPTH(type) <= CV_64F );
    type = CV_MAT_TYPE(type);
    m.type = CV_MAT_MAGIC_VAL | CV_MAT_CONT_FLAG | type;
    m.cols = cols;
    m.rows = rows;
    m.step = m.cols*CV_ELEM_SIZE(type);
    m.data.ptr = (uchar*)data;
    m.refcount = NULL;
    m.hdr_refcount = 0;

    return m;
}











CV_INLINE ?double ?cvmGet( const CvMat* mat, int row, int col )
{／／低效率访问！
? ? int type;


? ? type = CV_MAT_TYPE(mat->type);
? ? assert( (unsigned)row < (unsigned)mat->rows &&
? ? ? ? ? ? (unsigned)col < (unsigned)mat->cols );


? ? if( type == CV_32FC1 )
? ? ? ? return ((float*)(void*)(mat->data.ptr + (size_t)mat->step*row))[col];
? ? else
? ? {
? ? ? ? assert( type == CV_64FC1 );
? ? ? ? return ((double*)(void*)(mat->data.ptr + (size_t)mat->step*row))[col];
? ? }
}




CV_INLINE ?void ?cvmSet( CvMat* mat, int row, int col, double value )
{
? ? int type;
? ? type = CV_MAT_TYPE(mat->type);
? ? assert( (unsigned)row < (unsigned)mat->rows &&
? ? ? ? ? ? (unsigned)col < (unsigned)mat->cols );


? ? if( type == CV_32FC1 )
? ? ? ? ((float*)(void*)(mat->data.ptr + (size_t)mat->step*row))[col] = (float)value;
? ? else
? ? {
? ? ? ? assert( type == CV_64FC1 );
? ? ? ? ((double*)(void*)(mat->data.ptr + (size_t)mat->step*row))[col] = (double)value;
? ? }
}
typedef struct CvMatND
{
? ? int type;
? ? int dims;


? ? int* refcount;
? ? int hdr_refcount;


? ? union
? ? {
? ? ? ? uchar* ptr;
? ? ? ? float* fl;
? ? ? ? double* db;
? ? ? ? int* i;
? ? ? ? short* s;
? ? } data;


? ? struct
? ? {
? ? ? ? int size;
? ? ? ? int step;
? ? }
? ? dim[CV_MAX_DIM];
}
CvMatND;
/* Basic element of the file storage - scalar or collection: */
typedef struct CvFileNode
{
? ? int tag;
? ? struct CvTypeInfo* info; /* type information
? ? ? ? ? ? (only for user-defined object, for others it is 0) */
? ? union
? ? {
? ? ? ? double f; /* scalar floating-point number */
? ? ? ? int i; ? ?/* scalar integer number */
? ? ? ? CvString str; /* text string */
? ? ? ? CvSeq* seq; /* sequence (ordered collection of file nodes) */
? ? ? ? CvFileNodeHash* map; /* map (collection of named file nodes) */
? ? } data;
}
CvFileNode;