Image Processing28（Point Polygon Test )

Goal

In this tutorial you will learn how to:

Use the OpenCV function cv::pointPolygonTest
使用OpenCV函数cv :: pointPolygonTest
点多边形测试？

Theory

Code

#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#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;
findContours( src, contours, RETR_TREE, CHAIN_APPROX_SIMPLE);

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 ); }
          //确定点是否在轮廓的内部。返回值分别为+1，-1和0.
     }

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 );

//下面这个函数是把图像绘制出来
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);

}

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