1、尋找凸包函式

void convexHull(InputArray Point,OutputArray hull,bool clockwise=false,bool returnPoints=true)

引數一：輸入的二維點集，可以是Mat或者是std：vector

引數二：輸出引數，函式呼叫後的輸出的凸包

引數三：為真輸出的凸包順時針方向，為假輸出的凸包逆時針

引數四：為真返回個凸包的各個點，為假返回凸包的指數。若輸出陣列型別是std:vector是忽略該標誌

示例：

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
#define WINDOW_NAME1 "【原始圖】"
#define WINDOW_NAME2 "【效果圖】"
using namespace std;
using namespace cv;

Mat g_srcImage,g_grayImage;
int g_Thresh =50;
int g_ThreshMax = 255;
RNG rng(12345);
Mat srcImage_copy = g_srcImage.clone();
Mat g_thresholdImage_output;
vector<vector<Point> >g_vContours;
vector<Vec4i>g_vHierarchy;

void on_ThreshChange(int,void *);
int main(int argc,char *argv[])
{
	if(argc!=2)
	{
		cout<<"input error"<<endl;
		return -1;
	}
	g_srcImage = imread(argv[1],1);
	if(g_srcImage.empty())
	{
		cout<<"read picture fail"<<endl;
		return -1;
	}
	namedWindow(WINDOW_NAME1,WINDOW_AUTOSIZE);
	namedWindow(WINDOW_NAME2,WINDOW_AUTOSIZE);
	imshow(WINDOW_NAME1,g_srcImage);
	cvtColor(g_srcImage,g_grayImage,COLOR_BGR2GRAY);
	blur(g_grayImage,g_grayImage,Size(3,3));
	
	createTrackbar("閾值：",WINDOW_NAME2,&g_Thresh,g_ThreshMax,on_ThreshChange);
	on_ThreshChange(0,0);
	
	waitKey(0);
	return 0;
}

void on_ThreshChange(int,void *)
{
	threshold(g_grayImage,g_thresholdImage_output,g_Thresh,255,THRESH_BINARY);
	findContours(g_thresholdImage_output,g_vContours,g_vHierarchy,RETR_TREE,CHAIN_APPROX_SIMPLE,Point(0,0));
	vector<vector<Point> > hull(g_vContours.size());
	for(int i=0;i<g_vContours.size();i++)
	{
		convexHull(Mat(g_vContours[i]),hull[i],false);
	}
	Mat drawing = Mat::zeros(g_thresholdImage_output.size(),CV_8UC3);
	for(unsigned int i=0;i<g_vContours.size();i++)
	{
		Scalar color = Scalar(rng.uniform(0,255),rng.uniform(0,255),rng.uniform(0,255));
		drawContours(drawing,g_vContours,i,color,1,8,vector<Vec4i>(),0,Point());
		drawContours(drawing,hull,i,color,1,8,vector<Vec4i>(),0,Point());
	}
	imshow(WINDOW_NAME2,drawing);
}