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# Shi-Tomasi corner detector

## Goal

In this tutorial you will learn how to:

- Use the function goodFeaturesToTrack to detect corners using the Shi-Tomasi method.

## Theory

## Code

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

    #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 maxCorners = 23;
    int maxTrackbar = 100;

    RNG rng(12345);
    char* source_window = "Image";

    /// Function header
    void goodFeaturesToTrack_Demo( int, void* );

    /**
     * @function main
     */
    int main( int argc, char** argv )
    {
      /// Load source image and convert it to gray
      src = imread( argv[1], 1 );
      cvtColor( src, src_gray, CV_BGR2GRAY );

      /// Create Window
      namedWindow( source_window, CV_WINDOW_AUTOSIZE );

      /// Create Trackbar to set the number of corners
      createTrackbar( "Max  corners:", source_window, &maxCorners, maxTrackbar, goodFeaturesToTrack_Demo );

      imshow( source_window, src );

      goodFeaturesToTrack_Demo( 0, 0 );

      waitKey(0);
      return(0);
    }

    /**
     * @function goodFeaturesToTrack_Demo.cpp
     * @brief Apply Shi-Tomasi corner detector
     */
    void goodFeaturesToTrack_Demo( int, void* )
    {
      if( maxCorners < 1 ) { maxCorners = 1; }

      /// Parameters for Shi-Tomasi algorithm
      vector<Point2f> corners;
      double qualityLevel = 0.01;
      double minDistance = 10;
      int blockSize = 3;
      bool useHarrisDetector = false;
      double k = 0.04;

      /// Copy the source image
      Mat copy;
      copy = src.clone();

      /// Apply corner detection
      goodFeaturesToTrack( src_gray,
                   corners,
                   maxCorners,
                   qualityLevel,
                   minDistance,
                   Mat(),
                   blockSize,
                   useHarrisDetector,
                   k );

      /// Draw corners detected
      cout<<"** Number of corners detected: "<<corners.size()<<endl;
      int r = 4;
      for( int 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 ); }

      /// Show what you got
      namedWindow( source_window, CV_WINDOW_AUTOSIZE );
      imshow( source_window, copy );
    }

## Explanation

## Result

## Help and Feedback

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- Ask a question on the Q&A forum.
- If you think something is missing or wrong in the documentation, please file a bug report.

### Navigation

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