OpenCV支持大量的轮廓、边缘、边界的相关函数，相应的函数有moments、HuMoments、findContours、drawContours、approxPolyDP、arcLength、boundingRect、contourArea、convexHull、fitEllipse、fitLine、isContourConvex、minAreaRect、minEnclosingCircle、mathcShapes、pointPolygonTest。
下面这个程序用到的函数有，简单介绍其功能如下：
findContours：找到图像中轮廓
approxPolyDP：对多边形曲线做近似
boundingRect：计算并返回包围轮廓点集的最小矩形
minEnclosingCircle：计算并返回包围轮廓点集的最小圆形及其半径
drawContours：根据轮廓点集和轮廓结构画出轮廓#include "stdafx.h"
#include "opencv2/highgui/highgui.hpp"#include "opencv2/imgproc/imgproc.hpp"#include <iostream>#include <stdio.h>#include <stdlib.h>using namespace cv;using namespace std;Mat src; Mat src_gray;int thresh = 100;int max_thresh = 255;RNG rng(12345);/// 函数声明void thresh_callback(int, void* );int main( int argc, char** argv ){/// 载入原图像, 返回3通道图像src = imread( "boundrect.jpg" );/// 转化成灰度图像并进行平滑cvtColor( src, src_gray, CV_BGR2GRAY );blur( src_gray, src_gray, Size(3,3) );/// 创建窗口char* source_window = "Source";namedWindow( source_window, CV_WINDOW_AUTOSIZE );imshow( source_window, src );createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback );thresh_callback( 0, 0 );waitKey(0);return(0);}void thresh_callback(int, void* ){Mat threshold_output;vector<vector<Point> > contours; //轮廓数组（非矩形数组），每个轮廓是一个Point型的vectorvector<Vec4i> hierarchy; //见下面findContours的解释/// 使用Threshold二值threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );/// 找到轮廓//contours参数为检测的轮廓数组，每一个轮廓用一个point类型的vector表示//hiararchy参数和轮廓个数相同，每个轮廓contours[ i ]对应4个hierarchy元素hierarchy[ i ][ 0 ] ~hierarchy[ i ][ 3 ]，//分别表示后一个轮廓、前一个轮廓、父轮廓、内嵌轮廓的索引编号，如果没有对应项，该值设置为负数。//CV_RETR_TREE：建立一个等级树结构的轮廓//findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );/// 多边形逼近轮廓 + 获取矩形和圆形边界框vector<vector<Point> > contours_poly( contours.size() );//近似后的轮廓点集vector<Rect> boundRect( contours.size() ); //包围点集的最小矩形vectorvector<Point2f>center( contours.size() ); //包围点集的最小圆形vectorvector<float>radius( contours.size() );//包围点集的最小圆形半径vectorfor( int i = 0; i < contours.size(); i++ ){approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );//对多边形曲线做适当近似，contours_poly[i]是输出的近似点集boundRect[i] = boundingRect( Mat(contours_poly[i]) ); //计算并返回包围轮廓点集的最小矩形minEnclosingCircle( contours_poly[i], center[i], radius[i] );//计算并返回包围轮廓点集的最小圆形及其半径}/// 画多边形轮廓 + 包围的矩形框 + 圆形框Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );for( int i = 0; i< contours.size(); i++ ){Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) ); //随机颜色// drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() );drawContours( drawing, contours_poly, i, color, 1, 8, hierarchy, 0, Point() ); //根据轮廓点集contours_poly和轮廓结构hierarchy画出轮廓rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 ); //画矩形，tl矩形左上角，br右上角circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );//画圆形}/// 显示在一个窗口namedWindow( "Contours", CV_WINDOW_AUTOSIZE );imshow( "Contours", drawing );}
