Image Processing25（Creating Bounding boxes and circles for contours )

Goal

In this tutorial you will learn how to:

• Use the OpenCV function cv::boundingRect
• 使用OpenCV函数cv :: boundingRect
• Use the OpenCV function cv::minEnclosingCircle
• 使用OpenCV函数cv :: minEnclosingCircle

Theory

Code

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
Mat src; Mat src_gray;
int thresh = 100;
int max_thresh = 255;
RNG rng(12345);
void thresh_callback(int, void* );
int main( int argc, char** argv )
{
  CommandLineParser parser( argc, argv, "{@input | lena.jpg | input image}" );
  src = imread( parser.get<String>( "@input" ), IMREAD_COLOR );
  if( src.empty() )
    {
      cout << "Could not open or find the image!\n" << endl;
      cout << "usage: " << argv[0] << " <Input image>" << endl;
      return -1;
    }
  cvtColor( src, src_gray, COLOR_BGR2GRAY );//灰度
  blur( src_gray, src_gray, Size(3,3) );//均值
  const char* source_window = "Source";
  namedWindow( source_window, 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;
  vector<Vec4i> hierarchy;
 
  threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
  findContours( threshold_output, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0) );
 
  vector<vector<Point> > contours_poly( contours.size() );
 
  vector<Rect> boundRect( contours.size() );
  vector<Point2f>center( contours.size() );
  vector<float>radius( contours.size() );
  for( size_t i = 0; i < contours.size(); i++ )
  {
    approxPolyDP( contours[i], contours_poly[i], 3, true );
    //2D点输入向量，存储结果（多边形曲线），精度，是否闭合
    boundRect[i] = boundingRect( contours_poly[i] );//输入
    minEnclosingCircle( contours_poly[i], center[i], radius[i] );
    //输入，输出圆心，输入半径
  }
  Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
  for( size_t i = 0; i< contours.size(); i++ )
  {
    Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
    drawContours( drawing, contours_poly, (int)i, color, 1, 8, vector<Vec4i>(), 0, Point() );
    rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
    //注意到左上角和右上角
    circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );
  }
  namedWindow( "Contours", WINDOW_AUTOSIZE );
  imshow( "Contours", drawing );
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

set(CMAKE_CXX_FLAGS "-std=c++11")
project( DisplayImage )
find_package( OpenCV REQUIRED )
include_directories( ${OpenCV_INCLUDE_DIRS} )
add_executable( DisplayImage main.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

install(TARGETS DisplayImage RUNTIME DESTINATION bin

Results