• 有哪些特征？它们有什么用？
• 使用函数 cornerHarris 通过 Harris-Stephens方法检测角点.

有哪些特征?

是指

• 匹配关键点 是指在场景中可以很容易识别出来的 特性 . 这些特性就是这里所说的 特征 。
• 因此,特征应该有什么样的特性呢?
  • 应该具有 可识别的独一无二性

图像特征类型

图像特征类型:

本教程涉及 角点 特征。

为什么角点是特殊的?

如何工作？

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>using namespace cv;
using namespace std;/// Global variables
Mat src, src_gray;
int thresh = 200;
int max_thresh = 255;char* source_window = "Source image";
char* corners_window = "Corners detected";/// Function header
void cornerHarris_demo( int, void* );/** @function main */
int main( int argc, char** argv )
{/// Load source image and convert it to graysrc = imread( argv[1], 1 );cvtColor( src, src_gray, CV_BGR2GRAY );/// Create a window and a trackbarnamedWindow( source_window, CV_WINDOW_AUTOSIZE );createTrackbar( "Threshold: ", source_window, &thresh, max_thresh, cornerHarris_demo );imshow( source_window, src );cornerHarris_demo( 0, 0 );waitKey(0);return(0);
}/** @function cornerHarris_demo */
void cornerHarris_demo( int, void* )
{Mat dst, dst_norm, dst_norm_scaled;dst = Mat::zeros( src.size(), CV_32FC1 );/// Detector parametersint blockSize = 2;int apertureSize = 3;double k = 0.04;/// Detecting cornerscornerHarris( src_gray, dst, blockSize, apertureSize, k, BORDER_DEFAULT );/// Normalizingnormalize( dst, dst_norm, 0, 255, NORM_MINMAX, CV_32FC1, Mat() );convertScaleAbs( dst_norm, dst_norm_scaled );/// Drawing a circle around cornersfor( 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 );}}}/// Showing the resultnamedWindow( corners_window, CV_WINDOW_AUTOSIZE );imshow( corners_window, dst_norm_scaled );
}