Opencv: pointPolygonTest函数使用

参考：
http://blog.csdn.net/fuyou25/article/details/53467204
https://docs.opencv.org/2.4/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=pointpolygontest#pointpolygontest
https://docs.opencv.org/2.4/doc/tutorials/imgproc/shapedescriptors/point_polygon_test/point_polygon_test.html

根据Opencv文档，pointPolygonTest的参数及解释如下：

函数形式

C++: double pointPolygonTest(InputArray contour, Point2f pt, bool measureDist)

函数作用

判断一个点是否在一个contour的内部还是外部。

参数解释

contour – 输入findContour提取到的边缘.pt – 需要检测的点.measureDist – 为真，则计算检测点到边缘的距离，为负值在外部，0在边上，正值在内部。为假，则返回-1（在contour外部）、0（在contour上）、1（在contour内部。

Demo(代码和示意图版权归Opencv所有，此处仅作示例，参考链接在文首）

#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 ){  /// Create an image  const int r = 100;  Mat src = Mat::zeros( Size( 4*r, 4*r ), CV_8UC1 );  /// Create a sequence of points to make a contour:  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 );  /// Draw it in src  for( int j = 0; j < 6; j++ )     { line( src, vert[j],  vert[(j+1)%6], Scalar( 255 ), 3, 8 ); }  /// Get the contours  vector<vector<Point> > contours; vector<Vec4i> hierarchy;  Mat src_copy = src.clone();  findContours( src_copy, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE);  /// Calculate the distances to the contour  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);  /// Depicting the  distances graphically  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; }          }     }  /// Create Window and show your results  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);}