角点检测集锦（Harris，Shi-Tomasi，亚像素级角点检测）原理及相关实现

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
Mat src, src_gray;
int thresh = 200;
int max_thresh = 255;
const char* source_window = "Source image";
const char* corners_window = "Corners detected";
void cornerHarris_demo( int, void* );
int main( int, char** argv )
{
  src = imread( argv[1], IMREAD_COLOR );
  cvtColor( src, src_gray, COLOR_BGR2GRAY );
  namedWindow( source_window, WINDOW_AUTOSIZE );
  createTrackbar( "Threshold: ", source_window, &thresh, max_thresh, cornerHarris_demo );
  imshow( source_window, src );
  cornerHarris_demo( 0, 0 );
  waitKey(0);
  return(0);
}
void cornerHarris_demo( int, void* )
{
  Mat dst, dst_norm, dst_norm_scaled;
  dst = Mat::zeros( src.size(), CV_32FC1 );
  int blockSize = 2;
  int apertureSize = 3;
  double k = 0.04;
  cornerHarris( src_gray, dst, blockSize, apertureSize, k, BORDER_DEFAULT );
  normalize( dst, dst_norm, 0, 255, NORM_MINMAX, CV_32FC1, Mat() );
  convertScaleAbs( dst_norm, dst_norm_scaled );
  for( int j = 0; j < dst_norm.rows ; j++ )
     { for( int i = 0; i < dst_norm.cols; i++ )
          {
            if( (int) dst_norm.at<float>(j,i) > thresh )
              {
               circle( dst_norm_scaled, Point( i, j ), 5,  Scalar(0), 2, 8, 0 );
              }
          }
     }
  namedWindow( corners_window, WINDOW_AUTOSIZE );
  imshow( corners_window, dst_norm_scaled );
}

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
Mat src, src_gray;
int maxCorners = 23;
int maxTrackbar = 100;
RNG rng(12345);
const char* source_window = "Image";
void goodFeaturesToTrack_Demo( int, void* );
int main( int, char** argv )
{
  src = imread( argv[1], IMREAD_COLOR );
  cvtColor( src, src_gray, COLOR_BGR2GRAY );
  namedWindow( source_window, WINDOW_AUTOSIZE );
  createTrackbar( "Max  corners:", source_window, &maxCorners, maxTrackbar, goodFeaturesToTrack_Demo );
  imshow( source_window, src );
  goodFeaturesToTrack_Demo( 0, 0 );
  waitKey(0);
  return(0);
}
void goodFeaturesToTrack_Demo( int, void* )
{
  if( maxCorners < 1 ) { maxCorners = 1; }
  vector<Point2f> corners;
  double qualityLevel = 0.01;
  double minDistance = 10;
  int blockSize = 3, gradiantSize = 3;
  bool useHarrisDetector = false;
  double k = 0.04;
  Mat copy;
  copy = src.clone();
  goodFeaturesToTrack( src_gray,
               corners,
               maxCorners,
               qualityLevel,
               minDistance,
               Mat(),
               blockSize,
               gradiantSize,
               useHarrisDetector,
               k );
  cout<<"** Number of corners detected: "<<corners.size()<<endl;
  int r = 4;
  for( size_t i = 0; i < corners.size(); i++ )
     { circle( copy, corners[i], r, Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255)), -1, 8, 0 ); }
  namedWindow( source_window, WINDOW_AUTOSIZE );
  imshow( source_window, copy );
}

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
Mat src, src_gray;
Mat myHarris_dst; Mat myHarris_copy; Mat Mc;
Mat myShiTomasi_dst; Mat myShiTomasi_copy;
int myShiTomasi_qualityLevel = 50;
int myHarris_qualityLevel = 50;
int max_qualityLevel = 100;
double myHarris_minVal; double myHarris_maxVal;
double myShiTomasi_minVal; double myShiTomasi_maxVal;
RNG rng(12345);
const char* myHarris_window = "My Harris corner detector";
const char* myShiTomasi_window = "My Shi Tomasi corner detector";
void myShiTomasi_function( int, void* );
void myHarris_function( int, void* );
int main( int, char** argv )
{
  src = imread( argv[1], IMREAD_COLOR );
  cvtColor( src, src_gray, COLOR_BGR2GRAY );
  int blockSize = 3; int apertureSize = 3;
  myHarris_dst = Mat::zeros( src_gray.size(), CV_32FC(6) );
  Mc = Mat::zeros( src_gray.size(), CV_32FC1 );
  cornerEigenValsAndVecs( src_gray, myHarris_dst, blockSize, apertureSize, BORDER_DEFAULT );
  /* calculate Mc */
  for( int j = 0; j < src_gray.rows; j++ )
     { for( int i = 0; i < src_gray.cols; i++ )
          {
            float lambda_1 = myHarris_dst.at<Vec6f>(j, i)[0];
            float lambda_2 = myHarris_dst.at<Vec6f>(j, i)[1];
            Mc.at<float>(j,i) = lambda_1*lambda_2 - 0.04f*pow( ( lambda_1 + lambda_2 ), 2 );
          }
     }
  minMaxLoc( Mc, &myHarris_minVal, &myHarris_maxVal, 0, 0, Mat() );
  /* Create Window and Trackbar */
  namedWindow( myHarris_window, WINDOW_AUTOSIZE );
  createTrackbar( " Quality Level:", myHarris_window, &myHarris_qualityLevel, max_qualityLevel, myHarris_function );
  myHarris_function( 0, 0 );
  myShiTomasi_dst = Mat::zeros( src_gray.size(), CV_32FC1 );
  cornerMinEigenVal( src_gray, myShiTomasi_dst, blockSize, apertureSize, BORDER_DEFAULT );
  minMaxLoc( myShiTomasi_dst, &myShiTomasi_minVal, &myShiTomasi_maxVal, 0, 0, Mat() );
  /* Create Window and Trackbar */
  namedWindow( myShiTomasi_window, WINDOW_AUTOSIZE );
  createTrackbar( " Quality Level:", myShiTomasi_window, &myShiTomasi_qualityLevel, max_qualityLevel, myShiTomasi_function );
  myShiTomasi_function( 0, 0 );
  waitKey(0);
  return(0);
}
void myShiTomasi_function( int, void* )
{
  myShiTomasi_copy = src.clone();
  if( myShiTomasi_qualityLevel < 1 ) { myShiTomasi_qualityLevel = 1; }
  for( int j = 0; j < src_gray.rows; j++ )
     { for( int i = 0; i < src_gray.cols; i++ )
          {
            if( myShiTomasi_dst.at<float>(j,i) > myShiTomasi_minVal + ( myShiTomasi_maxVal - myShiTomasi_minVal )*myShiTomasi_qualityLevel/max_qualityLevel )
              { circle( myShiTomasi_copy, Point(i,j), 4, Scalar( rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255) ), -1, 8, 0 ); }
          }
     }
  imshow( myShiTomasi_window, myShiTomasi_copy );
}
void myHarris_function( int, void* )
{
  myHarris_copy = src.clone();
  if( myHarris_qualityLevel < 1 ) { myHarris_qualityLevel = 1; }
  for( int j = 0; j < src_gray.rows; j++ )
     { for( int i = 0; i < src_gray.cols; i++ )
          {
            if( Mc.at<float>(j,i) > myHarris_minVal + ( myHarris_maxVal - myHarris_minVal )*myHarris_qualityLevel/max_qualityLevel )
              { circle( myHarris_copy, Point(i,j), 4, Scalar( rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255) ), -1, 8, 0 ); }
          }
     }
  imshow( myHarris_window, myHarris_copy );
}

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
Mat src, src_gray;
int maxCorners = 10;
int maxTrackbar = 25;
RNG rng(12345);
const char* source_window = "Image";
void goodFeaturesToTrack_Demo( int, void* );
int main( int, char** argv )
{
  src = imread( argv[1], IMREAD_COLOR );
  cvtColor( src, src_gray, COLOR_BGR2GRAY );
  namedWindow( source_window, WINDOW_AUTOSIZE );
  createTrackbar( "Max  corners:", source_window, &maxCorners, maxTrackbar, goodFeaturesToTrack_Demo );
  imshow( source_window, src );
  goodFeaturesToTrack_Demo( 0, 0 );
  waitKey(0);
  return(0);
}
void goodFeaturesToTrack_Demo( int, void* )
{
  if( maxCorners < 1 ) { maxCorners = 1; }
  vector<Point2f> corners;
  double qualityLevel = 0.01;
  double minDistance = 10;
  int blockSize = 3, gradiantSize = 3;
  bool useHarrisDetector = false;
  double k = 0.04;
  Mat copy;
  copy = src.clone();
  goodFeaturesToTrack( src_gray,
               corners,
               maxCorners,
               qualityLevel,
               minDistance,
               Mat(),
               blockSize,
               gradiantSize,
               useHarrisDetector,
               k );
  cout<<"** Number of corners detected: "<<corners.size()<<endl;
  int r = 4;
  for( size_t i = 0; i < corners.size(); i++ )
     { circle( copy, corners[i], r, Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255)), -1, 8, 0 ); }
  namedWindow( source_window, WINDOW_AUTOSIZE );
  imshow( source_window, copy );
  Size winSize = Size( 5, 5 );
  Size zeroZone = Size( -1, -1 );
  TermCriteria criteria = TermCriteria( TermCriteria::EPS + TermCriteria::COUNT, 40, 0.001 );
  cornerSubPix( src_gray, corners, winSize, zeroZone, criteria );
  for( size_t i = 0; i < corners.size(); i++ )
     { cout<<" -- Refined Corner ["<<i<<"]  ("<<corners[i].x<<","<<corners[i].y<<")"<<endl; }