由于项目需要，要对图像中的最大连通域进行标定，并且存储。首先需要使用cvFindCountour对边缘进行标定，其实它的原理就是连通域的边缘提取；其次就是对连通域进行大小判断找出最大的连通域；最后当然就是进行Rect并且ROI了。如果有需要可以进行存储。直接上源码吧。

#include "cv.h"#include "cxcore.h"#include "highgui.h" int main( int argc, char** argv ){ //声明IplImage指针 IplImage* pImg = cvLoadImage("black.bmp",0); IplImage* pContourImg = NULL; CvMemStorage * storage = cvCreateMemStorage(0); CvSeq * contour = 0; CvSeq *contmax = 0; int mode = CV_RETR_EXTERNAL; cvShowImage( "src", pImg ); //为轮廓显示图像申请空间 //3通道图像，以便用彩色显示 pContourImg = cvCreateImage(cvGetSize(pImg),  IPL_DEPTH_8U,  3); //copy source image and convert it to BGR image cvCvtColor(pImg, pContourImg, CV_GRAY2BGR); //查找contour cvFindContours( pImg, storage, &contour, sizeof(CvContour),  mode, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0)); //将轮廓画出    cvDrawContours(pContourImg, contour,  CV_RGB(255,0,0), CV_RGB(255, 0, 0),  2, 2, 8, cvPoint(0,0)); int area,maxArea = 10;//设面积最大值大于10Pixel for(;contour;contour = contour->h_next) {  area = fabs(cvContourArea( contour, CV_WHOLE_SEQ )); //获取当前轮廓面积  printf("area == %lf\n", area);  if(area > maxArea)  {   contmax = contour;   maxArea = area;  } } CvRect aRect = cvBoundingRect( contmax, 0 ); cvSetImageROI( pContourImg,aRect); //显示图像 cvShowImage( "contour", pContourImg ); cvSaveImage("contour.bmp",pContourImg); cvWaitKey(0); //销毁窗口 cvDestroyWindow( "src" ); cvDestroyWindow( "contour" ); //释放图像 cvReleaseImage( &pImg ); cvReleaseImage( &pContourImg ); cvReleaseMemStorage(&storage); return 0;}

处理前的连通域

处理后的连通域

1. a. 二值化
2. b. 得到轮廓的个数
3. c. 将面积小于100的轮廓删除
4. d. 将宽、高 比例小于1的轮廓删除
5. e. 把面积最大的米粒用红色框框画出来

#include <stdio.h>#include <cv.h>#include <cxcore.h>#include <highgui.h>#pragma comment(lib, "ml.lib")#pragma comment(lib, "cv.lib")#pragma comment(lib, "cvaux.lib")#pragma comment(lib, "cvcam.lib")#pragma comment(lib, "cxcore.lib")#pragma comment(lib, "cxts.lib")#pragma comment(lib, "highgui.lib")#pragma comment(lib, "cvhaartraining.lib")int main( int argc, char** argv )  {   IplImage* src;   src=cvLoadImage("black.jpg",CV_LOAD_IMAGE_GRAYSCALE);   IplImage* dst = cvCreateImage( cvGetSize(src), 8, 3 );   CvMemStorage* storage = cvCreateMemStorage(0);   CvSeq* contour = 0;   cvThreshold( src, src,120, 255, CV_THRESH_BINARY );//二值化    cvNamedWindow( "Source", 1 );   cvShowImage( "Source", src );   //提取轮廓    cvFindContours( src, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE );   cvZero( dst );//清空数组    CvSeq* _contour =contour;    double maxarea=0;   double minarea=100;   int n=-1,m=0;//n为面积最大轮廓索引，m为迭代索引    for( ; contour != 0; contour = contour->h_next )   {    double tmparea=fabs(cvContourArea(contour));    if(tmparea < minarea)     {     cvSeqRemove(contour,0); //删除面积小于设定值的轮廓      continue;    }    CvRect aRect = cvBoundingRect( contour, 0 );     if ((aRect.width/aRect.height)<1)    {     cvSeqRemove(contour,0); //删除宽高比例小于设定值的轮廓      continue;    }    if(tmparea > maxarea)    {     maxarea = tmparea;     n=m;    }    m++;    //  CvScalar color = CV_RGB( rand()&255, rand()&255, rand()&255 );//创建一个色彩值     CvScalar color = CV_RGB( 0, 255,255 );    //max_level 绘制轮廓的最大等级。如果等级为0，绘制单独的轮廓。如果为1，绘制轮廓及在其后的相同的级别下轮廓。     //如果值为2，所有的轮廓。如果等级为2，绘制所有同级轮廓及所有低一级轮廓，诸此种种。     //如果值为负数，函数不绘制同级轮廓，但会升序绘制直到级别为abs(max_level)-1的子轮廓。      cvDrawContours( dst, contour, color, color, -1, 1, 8 );//绘制外部和内部的轮廓    }   contour =_contour; /*int k=0;*/   int count=0;   for( ; contour != 0; contour = contour->h_next )   {    count++;    double tmparea=fabs(cvContourArea(contour));    if (tmparea==maxarea /*k==n*/)    {     CvScalar color = CV_RGB( 255, 0, 0);     cvDrawContours( dst, contour, color, color, -1, 1, 8 );    }    /*k++;*/   }   printf("The total number of contours is:%d",count);   cvNamedWindow( "Components", 1 );   cvShowImage( "Components", dst );   cvWaitKey(0);   cvDestroyWindow( "Source" );   cvReleaseImage(&src);   cvDestroyWindow( "Components" );   cvReleaseImage(&dst);   return 0;  }  

以下是结果：