CvMemStorage,CvSeq,CvContour和cvFindContour的分析

CvSeq源码

#define CV_TREE_NODE_FIELDS(node_type)                          /    int       flags;         /* micsellaneous flags */          /    int       header_size;   /* size of sequence header */      /    struct    node_type* h_prev; /* previous sequence */        /    struct    node_type* h_next; /* next sequence */            /    struct    node_type* v_prev; /* 2nd previous sequence */    /    struct    node_type* v_next  /* 2nd next sequence *//*   Read/Write sequence.   Elements can be dynamically inserted to or deleted from the sequence.*/#define CV_SEQUENCE_FIELDS()                                            /    CV_TREE_NODE_FIELDS(CvSeq);                                         /    int       total;          /* total number of elements */            /    int       elem_size;      /* size of sequence element in bytes */   /    char*     block_max;      /* maximal bound of the last block */     /    char*     ptr;            /* current write pointer */               /    int       delta_elems;    /* how many elements allocated when the seq grows */  /    CvMemStorage* storage;    /* where the seq is stored */             /    CvSeqBlock* free_blocks;  /* free blocks list */                    /    CvSeqBlock* first; /* pointer to the first sequence block */typedef struct CvSeq{    CV_SEQUENCE_FIELDS()}CvSeq;

CvSeq本身就是可动态增长序列，创建一个CvSeq需要先申请一块儿空间，需要用到CvMemStorage（动态内存存储及操作）

CvMemStorage  typedef struct CvMemStorage  {  struct CvMemBlock* bottom;/* first allocated block */  struct CvMemBlock* top; /* the current memory block - top of the stack */  struct CvMemStorage* parent; /* borrows new blocks from */  int block_size; /* block size */  int free_space; /* free space in the top block (in bytes) */  } CvMemStorage; 

关于这个数据结构，有一篇博客讲的非常清楚

http://blog.csdn.net/myeclipseworkspace/article/details/6299281

用完之后要手动释放，否则可能会内存泄露，cvClearMemStorage（storage）；

我得理解，cvCreateSeq（int seq_flags,int header_size,int elem_size,CvMemStorage* storage）函数根据参数设定的大小，创建了一个序列，这个序列是树上的一个节点，可动态增加。

CvContour发展自序列

typedef struct CvContour{   CV_CONTOUR_FIELDS()}CvContour;

#define CV_CONTOUR_FIELDS (   )   Value:CV_SEQUENCE_FIELDS()     \    CvRect rect;             \    int color;               \    int reserved[3];

cvFindContours
int iCount=cvFindContours( imgDst, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_CODE );
只要将查找到的第一个轮廓存入创建的树的结点，便可利用指针找到其他的结点，找到的轮廓是点集，而非封闭的曲线。