.. _bounding_rects_circles:


创建包围轮廓的矩形和圆形边界框
*************************************************

目标
=====

在这节教程中您将学到:

.. container:: enumeratevisibleitemswithsquare

   * 使用OpenCV函数 :bounding_rect:`boundingRect <>` 来计算包围轮廓的矩形框.
   * 使用OpenCV函数 :min_enclosing_circle:`minEnclosingCircle <>` 来计算完全包围已有轮廓最小圆.
          

原理
======

代码
====

下面是本节教程源码. 你也可以从 `这里 <https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp>`_ 下载.

.. code-block:: cpp 

   #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* );

   /** @主函数 */
   int main( int argc, char** argv )
   {
     /// 载入原图像, 返回3通道图像
     src = imread( argv[1], 1 );

     /// 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);
   }

   /** @thresh_callback 函数 */
   void thresh_callback(int, void* )
   {
     Mat threshold_output;
     vector<vector<Point> > contours;
     vector<Vec4i> hierarchy;

     /// 使用Threshold检测边缘
     threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
     /// 找到轮廓  
     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() );
     vector<Rect> boundRect( contours.size() );
     vector<Point2f>center( contours.size() );
     vector<float>radius( contours.size() );

     for( int i = 0; i < contours.size(); i++ )
        { approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true ); 
          boundRect[i] = boundingRect( Mat(contours_poly[i]) ); 
          minEnclosingCircle( contours_poly[i], center[i], radius[i] );
        } 


     /// 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) );
          drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() ); 
          rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
          circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );
        }

     /// 显示在一个窗口
     namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
     imshow( "Contours", drawing );
   }

代码说明
============

结果
======

#. 如下所示:

   ========== ==========  
    |BRC_0|   |BRC_1|   
   ========== ==========   

   .. |BRC_0|  image:: images/Bounding_Rects_Circles_Source_Image.jpg
                    :align: middle

   .. |BRC_1|  image:: images/Bounding_Rects_Circles_Result.jpg
                    :align: middle   

翻译者
===============
guoming0000@ `OpenCV中文网站 <http://www.opencv.org.cn>`_ <guoming0000@sina.com>