这个好像是骨头什么的，但是要求轮廓闭合，于是对图片进行一下膨胀操作，再次检测轮廓就好了。

// A closed contour.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

// FindRotation-angle.cpp : 定义控制台应用程序的入口点。
//

// findContours.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

?

#include
#include
#include
#include
#include
#include
//#include "highlight"
//#include "highgui.h"

#pragma comment(lib,"opencv_core2410d.lib")? ? ? ?
#pragma comment(lib,"opencv_highgui2410d.lib")? ? ? ?
#pragma comment(lib,"opencv_imgproc2410d.lib")?

#define PI 3.1415926

using namespace std;
using namespace cv;

int main()
{
?// Read input binary image

?char *image_name = "test.bmp";
?cv::Mat image = cv::imread(image_name);
?if (!image.data)
? return 0;

?

?
?// 从文件中加载原图?
? // IplImage *pSrcImage = cvLoadImage(image_name, CV_LOAD_IMAGE_UNCHANGED);?
? Mat gray(image.size(),CV_8U);
? ?
? cvtColor(image,gray,CV_BGR2GRAY);
? // 转为2值图
? threshold(gray,gray,145,255,cv::THRESH_BINARY_INV);
?//cvThreshold(pSrcImage,pSrcImage,145,255,cv::THRESH_BINARY_INV);
? ?
?
? ? //image = gray;

? ? cv::namedWindow("Binary Image");
? ? cv::imshow("Binary Image",gray);

?

? ? cv::Mat element(5,5,CV_8U,cv::Scalar(255));

? ? cv::dilate(gray,gray,element);
? ? //cv::erode(image,image,element);

? ? cv::namedWindow("dilate Image");
? ? cv::imshow("dilate Image",gray);

?// Get the contours of the connected components
?std::vector> contours;

?cv::findContours(gray,
? contours, // a vector of contours
? CV_RETR_EXTERNAL , // retrieve the external contours
? CV_CHAIN_APPROX_NONE); // retrieve all pixels of each contours

?// Print contours' length
?std::cout << "Contours: " << contours.size() << std::endl;
?std::vector>::const_iterator itContours= contours.begin();
?for ( ; itContours!=contours.end(); ++itContours)
?{

? std::cout << "Size: " << itContours->size() << std::endl;
?}

?// draw black contours on white image
?cv::Mat result(image.size(),CV_8U,cv::Scalar(255));
?cv::drawContours(result,contours,
? -1, // draw all contours
? cv::Scalar(0), // in black
? 2); // with a thickness of 2

?cv::namedWindow("Contours");
?cv::imshow("Contours",result);

?

?

?

?

?// Eliminate too short or too long contours

?/*
?int cmin= 100;? // minimum contour length
?int cmax= 1000; // maximum contour length
?std::vector>::const_iterator itc= contours.begin();
?while (itc!=contours.end()) {

? if (itc->size() < cmin || itc->size() > cmax)
? ?itc= contours.erase(itc);
? else
? ?++itc;
?}
?
?*/

?// draw contours on the original image
?cv::Mat original= cv::imread(image_name);
?cv::drawContours(original,contours,
? -1, // draw all contours
? cv::Scalar(255,255,0), // in white
? 2); // with a thickness of 2

?cv::namedWindow("Contours on Animals");
?cv::imshow("Contours on Animals",original);

?

?// Let's now draw black contours on white image
?result.setTo(cv::Scalar(255));
?cv::drawContours(result,contours,
? -1, // draw all contours
? cv::Scalar(0), // in black
? 1); // with a thickness of 1
?image= cv::imread("binary.bmp",0);

?// testing the bounding box
?

?

?std::vector>::const_iterator itc_rec= contours.begin();
?while (itc_rec!=contours.end())
?{
? cv::Rect r0= cv::boundingRect(cv::Mat(*(itc_rec)));
? cv::rectangle(result,r0,cv::Scalar(0),2);
? ?++itc_rec;
?}

?/*
?// testing the enclosing circle
?float radius;
?cv::Point2f center;
?cv::minEnclosingCircle(cv::Mat(contours[1]),center,radius);
?cv::circle(result,cv::Point(center),static_cast(radius),cv::Scalar(0),2);