直接贴代码了。在写的时候借鉴了网上的一些代码，可是忘记保留链接了，所以此处向可能的贡献者致谢。

#include <cv.h>   
#include <highgui.h>   
#include <vector>   
#include <algorithm>   
using namespace std;  
  
#pragma comment( lib, "cv.lib" )   
#pragma comment( lib, "cxcore.lib" )   
#pragma comment( lib, "highgui.lib" )   
  
int main()  
{  
    IplImage *src = cvLoadImage("lena.jpg", CV_LOAD_IMAGE_COLOR);  
    cvNamedWindow("原始图像");  
    cvShowImage("原始图像", src);  
  
    IplImage* dst=cvCreateImage(cvSize(src->width,src->height),IPL_DEPTH_8U,1);   
    cvCvtColor(src,dst,CV_BGR2GRAY);  
    cvNamedWindow("灰度图像");  
    cvShowImage("灰度图像", src);  
  
    cvThreshold(dst, dst, 0.0, 255.0, CV_THRESH_BINARY | CV_THRESH_OTSU);//OTSU二值化   
    IplConvKernel *element = cvCreateStructuringElementEx(5, 5, 0, 0, CV_SHAPE_ELLIPSE);  
    cvMorphologyEx(dst, dst, NULL, element, CV_MOP_OPEN);//开运算，去除比结构元素小的点   
    cvReleaseStructuringElement(&element);  
    cvNamedWindow("二值图像");  
    cvShowImage("二值图像", dst);  
      
    int w,h;  
    CvSize sz = cvGetSize(dst);  
      
    int color = 254;//不对0计数，不可能为255，所以254   
    for (w=0; w<sz.width; w++)  
    {  
        for (h=0; h<sz.height; h++)  
        {  
            if (color > 0)  
            {  
                if (CV_IMAGE_ELEM(dst, unsigned char, h, w) == 255)  
                {  
                    //把连通域标记上颜色   
                    cvFloodFill(dst, cvPoint(w,h), CV_RGB( color,color,color));  
                    color--;  
                }  
            }  
        }  
    }  
    cvNamedWindow("标记颜色后的图像");  
    cvShowImage("标记颜色后的图像", dst);  
      
    int colorsum[255] = {0};  
    for (w=0; w<sz.width; w++)  
    {  
        for (h=0; h<sz.height; h++)  
        {  
            if (CV_IMAGE_ELEM(dst, unsigned char, h, w) > 0)  
            {  
                colorsum[CV_IMAGE_ELEM(dst, unsigned char, h, w)]++;//统计每种颜色的数量   
            }  
        }  
    }  
    vector<int> v1(colorsum, colorsum+255);//用数组初始化vector   
    //求出最多数量的染色，注意max_element的使用方法   
    int maxcolorsum = max_element(v1.begin(), v1.end()) - v1.begin();  
    printf("%d\n",maxcolorsum);  
  
    for (w=0; w<sz.width; w++)  
    {  
        for (h=0; h<sz.height; h++)  
        {  
            if (CV_IMAGE_ELEM(dst, unsigned char, h, w) == maxcolorsum)  
            {  
                CV_IMAGE_ELEM(dst, unsigned char, h, w) = 255;  
            }  
            else  
            {  
                CV_IMAGE_ELEM(dst, unsigned char, h, w) = 0;  
            }  
        }  
    }  
    cvNamedWindow("最大连通域图");  
    cvShowImage("最大连通域图", dst);  
      
    cvWaitKey(0);   
    cvDestroyAllWindows();  
    cvReleaseImage(&src);  
    cvReleaseImage(&dst);  
      
    return 0;  
}  

测试图像采用标准的Lena图像，测试结果为：