根据朋友给的一份原理写的 感觉还挺清楚

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
using namespace cv;

#define MAXWIDTH 352
#define MAXHEIGHT 288

typedef struct PTNode{ 
    int data;
    int parent;
}PTNode;


void GetCCL(Mat &imgsrc, Mat &imgdst)
{

    PTNode nodes[MAXWIDTH * MAXHEIGHT]; //线性树 数据的位置 与 数据本身 相同 即 nodes[x].data = x   
    memset(nodes, 0, MAXWIDTH * MAXHEIGHT * sizeof(PTNode));
    int nodenum = 0;
    int row, col;
    nodes[0].data = 0;
    nodes[0].parent = -1;
    for(row = 0; row < imgsrc.rows; row++)
    {
        for(col = 0; col < imgsrc.cols; col++)
        {
            if(imgsrc.at<uchar>(row, col) == 0) //像素为0的认为是背景 全黑色
            {
                imgdst.at<uchar>(row, col) = 0;
            }
            else //前景
            {
                if(row != 0 && col != 0) //不是边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row, col - 1)) // 判断 先左 后上 
                    {
                        imgdst.at<uchar>(row, col) = imgdst.at<uchar>(row, col - 1);  //如果和左边相同 标号和左边相同
                        if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col) && imgdst.at<uchar>(row, col) != imgdst.at<uchar>(row - 1, col)) //同时与左边 上边相连  且两个序号不同
                        {
                            imgdst.at<uchar>(row, col) = (imgdst.at<uchar>(row, col) > imgdst.at<uchar>(row - 1, col)) ? imgdst.at<uchar>(row - 1, col) : imgdst.at<uchar>(row, col);  //取小的编号

                            PTNode nodetmp1, nodetmp2;
                            nodetmp1 = nodes[imgdst.at<uchar>(row, col - 1)];
                            nodetmp2 = nodes[imgdst.at<uchar>(row - 1, col)];
                            while(nodetmp1.parent != -1)
                            {
                                nodetmp1 = nodes[nodetmp1.parent];
                            }
                            while(nodetmp2.parent != -1)
                            {
                                nodetmp2 = nodes[nodetmp2.parent];
                            }
                            if(nodetmp2.data > nodetmp1.data)  //小的序号做parent 大序号做child
                            {
                                nodes[nodetmp2.data].parent = nodetmp1.data;  //这里一定要对nodes中的值修改， 直接写nodetmp2.parent = nodetmp1.data 是不行的因为nodetmp2只是一个局部变量 nodes[]里的值根本没有修改
                            }
                            else if(nodetmp2.data < nodetmp1.data)
                            {
                                nodes[nodetmp1.data].parent = nodetmp2.data;
                            }
                            
                        }
                    }
                    else if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col)) //仅与上面相同 序号等于上面
                    {
                        imgdst.at<uchar>(row, col) = imgdst.at<uchar>(row - 1, col);    
                    }
                    else //与两个方向的序号都不同 新建一个序号 序号与位置相同
                    {
                        nodenum++;  
                        imgdst.at<uchar>(row, col) = nodenum;
                        nodes[imgdst.at<uchar>(row, col)].parent = -1;
                        nodes[imgdst.at<uchar>(row, col)].data = imgdst.at<uchar>(row, col);
                    }
                }
                else if(row == 0 && col != 0) //横向边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row, col - 1))
                    {
                        imgdst.at<uchar>(row, col) = imgdst.at<uchar>(row, col - 1);
                    }
                    else
                    {
                        nodenum++;
                        imgdst.at<uchar>(row, col) = nodenum;
                        nodes[imgdst.at<uchar>(row, col)].parent = -1;
                        nodes[imgdst.at<uchar>(row, col)].data = imgdst.at<uchar>(row, col);
                    }
                }
                else if(col == 0 && row != 0) //竖向边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col))
                    {
                        imgdst.at<uchar>(row, col) = imgdst.at<uchar>(row - 1, col);
                    }
                    else
                    {
                        nodenum++;
                        imgdst.at<uchar>(row, col) = nodenum;
                        nodes[imgdst.at<uchar>(row, col)].parent = -1;
                        nodes[imgdst.at<uchar>(row, col)].data = imgdst.at<uchar>(row, col);
                    }
                }
                else //开始的（0 ，0）点 直接新建
                {
                    nodenum++;
                    imgdst.at<uchar>(row, col) = nodenum;
                    nodes[imgdst.at<uchar>(row, col)].parent = -1;
                    nodes[imgdst.at<uchar>(row, col)].data = imgdst.at<uchar>(row, col);
                }
            }

        }
    }

    //FILE * out = fopen("D:\dst.txt", "w");
    //for(row = 0; row < imgsrc.rows; row++)
    //{
    //    for(col = 0; col < imgsrc.cols; col++)
    //    {
    //        fprintf(out, "%d ", imgdst.at<uchar>(row, col));
    //    }
    //    fprintf(out, "
");
    //}
    //把森林中每一个颗树都标成统一的颜色
    for(row = 0; row < imgsrc.rows; row++)
    {
        for(col = 0; col < imgsrc.cols; col++)
        {
            PTNode nodetmp = nodes[imgdst.at<uchar>(row, col)];  
            while(nodetmp.parent != -1)
            {
                nodetmp = nodes[nodetmp.parent];
            }
            imgdst.at<uchar>(row, col) = nodetmp.data * 52 % 255; //随意设个颜色显示
        }
    }

}

void main()
{
    IplImage* img = cvLoadImage("D:\Users\CCL\1.jpg", 0);
    IplImage* imgdst = cvCreateImage(cvGetSize(img), 8, 1);
    cvThreshold(img,img,125,255,0);
    cvShowImage("ori", img);
    Mat src(img), dst(imgdst);
    GetCCL(src, dst);
    cvShowImage("ccl", imgdst);
    cvWaitKey(0);
}

效果：

但是下面的图片出了问题：

 字母检测的很凌乱 

但是单独把一个字母拿出来 放大再检测就ok

找到上面多字母问题的原因了。问题出在下面一句：

imgdst.at<uchar>(row, col) = nodenum;

这里nodenum是可能超过255的 但是在传给imgdst时被强制转换成了uchar型，导致后面的结果出错。

用tmp.create(imgsrc.rows, imgsrc.cols, CV_32F);来修改错误。

修改后的代码如下：

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
using namespace cv;

#define MAXWIDTH 352
#define MAXHEIGHT 288

typedef struct PTNode{ 
    int data;
    int parent;
}PTNode;


void GetCCL(Mat &imgsrc, Mat &imgdst)
{
    Mat tmp;
    tmp.create(imgsrc.rows, imgsrc.cols, CV_32F);
    PTNode nodes[MAXWIDTH * MAXHEIGHT]; //线性树 数据的位置 与 数据本身 相同 即 nodes[x].data = x   
    memset(nodes, 0, MAXWIDTH * MAXHEIGHT * sizeof(PTNode));
    int nodenum = 0;
    int row, col;
    nodes[0].data = 0;
    nodes[0].parent = -1;
    for(row = 0; row < imgsrc.rows; row++)
    {
        for(col = 0; col < imgsrc.cols; col++)
        {
            if(imgsrc.at<uchar>(row, col) == 0) //像素为0的认为是背景 全黑色
            {
                tmp.at<int>(row, col) = 0;
            }
            else //前景
            {
                if(row != 0 && col != 0) //不是边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row, col - 1)) // 判断 先左 后上 
                    {
                        tmp.at<int>(row, col) = tmp.at<int>(row, col - 1);  //如果和左边相同 标号和左边相同
                        if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col) && tmp.at<int>(row, col) != tmp.at<int>(row - 1, col)) //同时与左边 上边相连  且两个序号不同
                        {
                            tmp.at<int>(row, col) = (tmp.at<int>(row, col) > tmp.at<int>(row - 1, col)) ? tmp.at<int>(row - 1, col) : tmp.at<int>(row, col);  //取小的编号

                            PTNode nodetmp1, nodetmp2;
                            nodetmp1 = nodes[tmp.at<int>(row, col - 1)];
                            nodetmp2 = nodes[tmp.at<int>(row - 1, col)];
                            while(nodetmp1.parent != -1)
                            {
                                nodetmp1 = nodes[nodetmp1.parent];
                            }
                            while(nodetmp2.parent != -1)
                            {
                                nodetmp2 = nodes[nodetmp2.parent];
                            }
                            if(nodetmp2.data > nodetmp1.data)  //小的序号做parent 大序号做child
                            {
                                nodes[nodetmp2.data].parent = nodetmp1.data;  //这里一定要对nodes中的值修改， 直接写nodetmp2.parent = nodetmp1.data 是不行的因为nodetmp2只是一个局部变量 nodes[]里的值根本没有修改
                            }
                            else if(nodetmp2.data < nodetmp1.data)
                            {
                                nodes[nodetmp1.data].parent = nodetmp2.data;
                            }
                            
                        }
                    }
                    else if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col)) //仅与上面相同 序号等于上面
                    {
                        tmp.at<int>(row, col) = tmp.at<int>(row - 1, col);    
                    }
                    else //与两个方向的序号都不同 新建一个序号 序号与位置相同
                    {
                        nodenum++;  
                        tmp.at<int>(row, col) = nodenum;
                        nodes[tmp.at<int>(row, col)].parent = -1;
                        nodes[tmp.at<int>(row, col)].data = tmp.at<int>(row, col);
                    }
                }
                else if(row == 0 && col != 0) //横向边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row, col - 1))
                    {
                        tmp.at<int>(row, col) = tmp.at<int>(row, col - 1);
                    }
                    else
                    {
                        nodenum++;
                        tmp.at<int>(row, col) = nodenum;   //这里有问题， nodenum可能会大于255 但是传给tmp.at<int>(row, col) 时被转换为uchar型 
                        nodes[tmp.at<int>(row, col)].parent = -1;
                        nodes[tmp.at<int>(row, col)].data = tmp.at<int>(row, col);
                    }
                }
                else if(col == 0 && row != 0) //竖向边界
                {
                    if(imgsrc.at<uchar>(row, col) == imgsrc.at<uchar>(row - 1, col))
                    {
                        tmp.at<int>(row, col) = tmp.at<int>(row - 1, col);
                    }
                    else
                    {
                        nodenum++;
                        tmp.at<int>(row, col) = nodenum;
                        nodes[tmp.at<int>(row, col)].parent = -1;
                        nodes[tmp.at<int>(row, col)].data = tmp.at<int>(row, col);
                    }
                }
                else //开始的（0 ，0）点 直接新建
                {
                    nodenum++;
                    tmp.at<int>(row, col) = nodenum;
                    nodes[tmp.at<int>(row, col)].parent = -1;
                    nodes[tmp.at<int>(row, col)].data = tmp.at<int>(row, col);
                }
            }

        }
    }

    //FILE * out = fopen("D:\dst.txt", "w");
    //for(row = 0; row < imgsrc.rows; row++)
    //{
    //    for(col = 0; col < imgsrc.cols; col++)
    //    {
    //        fprintf(out, "%d ", tmp.at<int>(row, col));
    //    }
    //    fprintf(out, "
");
    //}
    //把森林中每一个颗树都标成统一的颜色
    for(row = 0; row < imgsrc.rows; row++)
    {
        for(col = 0; col < imgsrc.cols; col++)
        {
            PTNode nodetmp = nodes[tmp.at<int>(row, col)];  
            while(nodetmp.parent != -1)
            {
                nodetmp = nodes[nodetmp.parent];
            }
            imgdst.at<uchar>(row, col) = nodetmp.data * 51 % 255; //随意设个颜色显示
        }
    }

}

void main()
{
    IplImage* img = cvLoadImage("D:\Users\2.jpg", 0);
    IplImage* imgdst = cvCreateImage(cvGetSize(img), 8, 1);
    cvThreshold(img,img,125,255,0);
    cvNot(img, img);
    cvShowImage("ori", img);
    Mat src(img), dst(imgdst);
    GetCCL(src, dst);
    cvShowImage("ccl", imgdst);
    cvWaitKey(0);
}

修正后结果就好了。有几个字母看起来像是丢了，其实是因为我随机选颜色，可能导致用黑色填充。