.. _point_polygon_test:

多边形测试
*******************

目的
=====

本教程指导用户:

.. container:: enumeratevisibleitemswithsquare

   * 使用OpenCV函数 :point_polygon_test:`pointPolygonTest <>` 
           

理论
======

代码
====

本教程代码如下所示. 用户也可以点击 `这里下载 <https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/ShapeDescriptors/pointPolygonTest_demo.cpp>`_

.. 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;

   /** @function main */
   int main( int argc, char** argv )
   {
     /// 创建一个图形     const int r = 100;
     Mat src = Mat::zeros( Size( 4*r, 4*r ), CV_8UC1 );

     /// 绘制一系列点创建一个轮廓:
     vector<Point2f> vert(6);

     vert[0] = Point( 1.5*r, 1.34*r );
     vert[1] = Point( 1*r, 2*r );
     vert[2] = Point( 1.5*r, 2.866*r );
     vert[3] = Point( 2.5*r, 2.866*r );
     vert[4] = Point( 3*r, 2*r );
     vert[5] = Point( 2.5*r, 1.34*r );

     /// 在src内部绘制
     for( int j = 0; j < 6; j++ )
        { line( src, vert[j],  vert[(j+1)%6], Scalar( 255 ), 3, 8 ); } 

     /// 得到轮廓
     vector<vector<Point> > contours; vector<Vec4i> hierarchy;
     Mat src_copy = src.clone();

     findContours( src_copy, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE);  

     /// 计算到轮廓的距离
     Mat raw_dist( src.size(), CV_32FC1 );

     for( int j = 0; j < src.rows; j++ )
        { for( int i = 0; i < src.cols; i++ )
             { raw_dist.at<float>(j,i) = pointPolygonTest( contours[0], Point2f(i,j), true ); }
        }

     double minVal; double maxVal;
     minMaxLoc( raw_dist, &minVal, &maxVal, 0, 0, Mat() );
     minVal = abs(minVal); maxVal = abs(maxVal);
  
     /// 图形化的显示距离
     Mat drawing = Mat::zeros( src.size(), CV_8UC3 );

     for( int j = 0; j < src.rows; j++ )
        { for( int i = 0; i < src.cols; i++ )
             { 
               if( raw_dist.at<float>(j,i) < 0 )
                 { drawing.at<Vec3b>(j,i)[0] = 255 - (int) abs(raw_dist.at<float>(j,i))*255/minVal; }
               else if( raw_dist.at<float>(j,i) > 0 )
                 { drawing.at<Vec3b>(j,i)[2] = 255 - (int) raw_dist.at<float>(j,i)*255/maxVal; }    
               else
                 { drawing.at<Vec3b>(j,i)[0] = 255; drawing.at<Vec3b>(j,i)[1] = 255; drawing.at<Vec3b>(j,i)[2] = 255; }     
             }
        }

     /// 创建窗口显示结果
     char* source_window = "Source";
     namedWindow( source_window, CV_WINDOW_AUTOSIZE );
     imshow( source_window, src );
     namedWindow( "Distance", CV_WINDOW_AUTOSIZE );
     imshow( "Distance", drawing );

     waitKey(0);
     return(0);
   }

解释
============

结果
======

#. 输出如下:

   ========== ==========  
    |PPT_0|   |PPT_1|   
   ========== ==========   

   .. |PPT_0|  image:: images/Point_Polygon_Test_Source_Image.png
                    :align: middle

   .. |PPT_1|  image:: images/Point_Polygon_Test_Result.jpg
                    :align: middle   

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