角点检测（特征值，Harris，FAST）

#include "stdafx.h"
#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/features2d/features2d.hpp>
using namespace cv;
using namespace std; 
  
int main (int argc, char **argv) 
{ 
  // (1)load a specified file as a 3-channel color image 
  const char *imagename = argc > 1 ? argv[1] : "../image/library.png"; 
  Mat eigen_img = imread(imagename); 
  if(!eigen_img.data) 
    return -1; 
  Mat harris_img = eigen_img.clone(); 
  Mat fast_img = eigen_img.clone(); 
  
  // (2)convert to a grayscale image and normalize it 
  Mat gray_img; 
  cvtColor(eigen_img, gray_img, CV_BGR2GRAY); 
  normalize(gray_img, gray_img, 0, 255, NORM_MINMAX); 
  
  // (3)detect and draw strong corners on the image based on Eigen Value 
  vector<Point2f> corners; 
  goodFeaturesToTrack(gray_img, corners, 80, 0.01, 5); 
  vector<Point2f>::iterator it_corner = corners.begin(); 
  for(; it_corner!=corners.end(); ++it_corner) { 
    circle(eigen_img, Point(it_corner->x, it_corner->y), 1, Scalar(0,200,255), -1); 
    circle(eigen_img, Point(it_corner->x, it_corner->y), 8, Scalar(0,200,255)); 
  } 
  
  // (4)detect and draw strong corners on the image using Harris detector 
  goodFeaturesToTrack(gray_img, corners, 80, 0.01, 3, Mat(), 3, true); 
  it_corner = corners.begin(); 
  for(; it_corner!=corners.end(); ++it_corner) { 
    circle(harris_img, Point(it_corner->x, it_corner->y), 1, Scalar(0,255,0), -1); 
    circle(harris_img, Point(it_corner->x, it_corner->y), 8, Scalar(0,255,0 )); 
  } 
  
  // (5)detect corners using high-speed corner detection; FAST 
  int threshold = 100; 
  bool nonmax = true; 
  vector<KeyPoint> keypoints; 
  FAST(gray_img, keypoints, threshold, nonmax); 
  vector<KeyPoint>::iterator it_kp = keypoints.begin(); 
  for(; it_kp!=keypoints.end(); ++it_kp) { 
    circle(fast_img, Point(it_kp->pt.x, it_kp->pt.y), 1, Scalar(50,0,255), -1); 
    circle(fast_img, Point(it_kp->pt.x, it_kp->pt.y), 8, Scalar(50,0,255)); 
  } 
  
  // (6)show destination images, and quit when any key pressed 
  namedWindow("EigenValue",CV_WINDOW_AUTOSIZE); 
  namedWindow("Harris",CV_WINDOW_AUTOSIZE); 
  namedWindow("Fast",CV_WINDOW_AUTOSIZE); 
  imshow("EigenValue", eigen_img); 
  imshow("Harris", harris_img); 
  imshow("Fast", fast_img); 
  waitKey(0); 
  
  return 0; 
}