OpenCV笔记 1

cvScalar() , takes one, two, three, or four arguments and assigns those arguments to the corresponding elements of val[] .　　set四个值

cvRealScalar() ; it takes one argument, which it assigns to val[0] while setting the other entries to 0.　　　　　　　　　　　　set第一个值，其余为0

cvScalarAll() , which takes a single argument but sets all four elements of val[] to that same argument.  　　　　　　　　　　全set成同一个值

For all intents andpurposes, an IplImage can be thought of as being derived from CvMat . Therefore, it is best to understand the (would-be) base class before attempting to understand the added complexities of the derived class. A third class, called CvArr , can be thought of as an abstract base class from which CvMat is itself derived. You will oft en see CvArr (or, more accurately, CvArr* ) in function prototypes. When it appears, it is acceptable to pass CvMat* or IplImage* to the routine.

32-bit floats ( CV_32FC1 ),

unsigned integer 8-bit triplets ( CV_8UC3 )

typedef struct CvMat {
    int type;
    int step;
    int* refcount;

    // for internal use only
    union {
        uchar* ptr;
        short* s;
        int*  i;
        float* fl;
        double* db;
    } data;
    union {
        int rows;
        int height;
     };
    union {
        int cols;
        int width;
     };
} CvMat;                        

cvCreateMatHeader() creates the CvMat structure without allocating memory for the data.
cvCreateData() handles the data allocation.

cvCreateMat()  =  cvCreateMatHeader() + cvCreateData() .

cvCloneMat(CvMat*) creates a new matrix from an existing one.*

cvReleaseMat(CvMat**)  release.

* cvCloneMat() and other OpenCV functions containing the word “clone” not only create a new header that
is identical to the input header, they also allocate a separate data area and copy the data from the source to
the new object.

* For the regular two-dimensional matrices discussed here, dimension zero (0) is always the “width” and dimension one (1) is always the height.

二维矩阵中，维度0通常是宽，维度1通常是高。

矩阵某个位置的元素：the location of any given point is given by the formula:

δ = ( row ) ⋅ N cols ⋅ N channels + ( col ) ⋅ N channels + ( channel)  通道

IplImage header structure

typedef struct _IplImage {
int nSize;
int ID;
int nChannels;
int alphaChannel;
int depth;
char colorModel[4];
char channelSeq[4];
int dataOrder;
int origin;
int align;
int width;
int height;
struct _IplROI* roi;
struct _IplImage* maskROI;
void* imageId;
struct _IplTileInfo* tileInfo;
int imageSize;
char* imageData;
int widthStep;
int BorderMode[4];
int BorderConst[4];
char* imageDataOrigin;
} IplImage;

Th e possible values for nChannels are 1, 2, 3, or 4.

origin : IPL_ORIGIN_TL or IPL_ORIGIN_BL （the origin of coordinates being located in either the upper-left or lower-left corners of the image, respectively.）

dataOrder： IPL_DATA_ORDER_PIXEL or IPL_DATA_ORDER_PLANE .（whether the data should be packed with multiple channels one aft er the other for each pixel (interleaved, the usual case), or rather all of the channels clustered into image planes with the planes placed one aft er another.）

ROI：感兴趣的区域

COI：感兴趣的通道 channel of interest