OpenCV  3.4.0 Open Source Computer Vision
Point Polygon Test

## Goal

In this tutorial you will learn how to:

## Code

This tutorial code's is shown lines below. You can also download it from here

#include <iostream>
using namespace cv;
using namespace std;
int main( void )
{
const int r = 100;
Mat src = Mat::zeros( Size( 4*r, 4*r ), CV_8UC1 );
vector<Point2f> vert(6);
vert[0] = Point( 3*r/2, static_cast<int>(1.34*r) );
vert[1] = Point( 1*r, 2*r );
vert[2] = Point( 3*r/2, static_cast<int>(2.866*r) );
vert[3] = Point( 5*r/2, static_cast<int>(2.866*r) );
vert[4] = Point( 3*r, 2*r );
vert[5] = Point( 5*r/2, static_cast<int>(1.34*r) );
for( int j = 0; j < 6; j++ )
{ line( src, vert[j], vert[(j+1)%6], Scalar( 255 ), 3, 8 ); }
vector<vector<Point> > contours;
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) = (float)pointPolygonTest( contours[0], Point2f((float)i,(float)j), true ); }
}
double minVal; double maxVal;
minMaxLoc( raw_dist, &minVal, &maxVal, 0, 0, Mat() );
minVal = abs(minVal); maxVal = abs(maxVal);
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] = (uchar)(255 - abs(raw_dist.at<float>(j,i))*255/minVal); }
else if( raw_dist.at<float>(j,i) > 0 )
{ drawing.at<Vec3b>(j,i)[2] = (uchar)(255 - 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; }
}
}
imshow( "Source", src );
imshow( "Distance", drawing );
waitKey(0);
return(0);
}

Here it is: