给轮廓画出矩形和圆形边界

OpenCV支持大量的轮廓、边缘、边界的相关函数,相应的函数有momentsHuMomentsfindContoursdrawContoursapproxPolyDParcLengthboundingRectcontourAreaconvexHullfitEllipsefitLineisContourConvexminAreaRectminEnclosingCircle mathcShapespointPolygonTest


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vector
  vector<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vector
  vector<Point2f>center( contours.size() );                               //包围点集的最小圆形vector
  vector<float>radius( contours.size() );                                   //包围点集的最小圆形半径vector
 
  for( 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 );
}


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