Leaning OpenCV:Corner Detection Using cvGoodFeaturesToTrack

转自：http://blog.csdn.net/utimes/archive/2010/07/05/5714224.aspx

 

Here’s an example opencv application which uses cvGoodFeaturesToTrack to detect corners in a webcam video feed.

 

// This code displays corners found by the opencv function
// GoodFeaturesToTrack (cvGoodFeaturesToTrack)
//
// Note: I commented out the corner detection using the Harris
// algorithm because my computer isn't fast enough to process
// both the Harris and the eigenvalue corners in real time.
// You can uncomment it and test for yourself.
//
#include <cv.h>
#include <highgui.h>
#include <stdio.h>
#include <time.h>
#define VIDEO_WINDOW   "Webcam"
#define CORNER_EIG     "Eigenvalue Corner Detection"
// Disable harris processing
//#define CORNER_HARRIS  "Corner Detection (Harris)"
#define USEC_PER_SEC 1000000L
CvScalar target_color[4] = { // in BGR order
  {{   0,   0, 255,   0 }},  // red
  {{   0, 255,   0,   0 }},  // green
  {{ 255,   0,   0,   0 }},  // blue
  {{   0, 255, 255,   0 }}   // yellow
};
// returns the number of usecs of (t2 - t1)
long time_elapsed (struct timeval &t1, struct timeval &t2) {
 long sec, usec;
 sec = t2.tv_sec - t1.tv_sec;
 usec = t2.tv_usec - t1.tv_usec;
 if (usec < 0) {
  --sec;
  usec = usec + USEC_PER_SEC;
 }
 return sec*USEC_PER_SEC + usec;
}
struct timeval start_time;
struct timeval end_time;
void start_timer() {
 struct timezone tz;
 gettimeofday (&start_time, &tz);
}
long end_timer() {
 struct timezone tz;
 gettimeofday (&end_time, &tz);
 return time_elapsed(start_time, end_time);
}
// A Simple Camera Capture Framework
int main(int argc, char *argv[]) {
 long harris_time;
 long eig_time;
 CvCapture* capture = 0;
 IplImage* curr_frame = 0; // current video frame
 IplImage* gray_frame = 0; // grayscale version of current frame
 int w, h; // video frame size
 IplImage* eig_image = 0;
 IplImage* temp_image = 0;
 // Disable harris processing
 //IplImage* harris_eig_image = 0;
 //IplImage* harris_temp_image = 0;
 
 // Pick one of these capture methods:
 // You must have compiled opencv with ffmpeg enabled
 // to use a web stream!
 //capture = cvCaptureFromFile(
 //  "http://user:[email protected]:81/img/video.mjpeg");
 //capture = cvCaptureFromAVI(
 //  "http://user:[email protected]:81/img/video.mjpeg");
 
 // Capture from a webcam
 capture = cvCaptureFromCAM(CV_CAP_ANY);
 //capture = cvCaptureFromCAM(0); // capture from video device #0
 if ( !capture) {
  fprintf(stderr, "ERROR: capture is NULL... Exiting/n");
  //getchar();
  return -1;
 }
 
 // Create a window in which the captured images will be presented
 cvNamedWindow(VIDEO_WINDOW, 0); // allow the window to be resized
 
 cvNamedWindow(CORNER_EIG, 0); // allow the window to be resized
 cvMoveWindow(CORNER_EIG, 330, 0);
 
 // Disable harris processing
 //cvNamedWindow(CORNER_HARRIS, 0); // allow the window to be resized
 //cvMoveWindow(CORNER_HARRIS, 660, 0);
 
 // Show the image captured from the camera in the window and repeat
 while (true) {
  
  // Get one frame
  curr_frame = cvQueryFrame(capture);
  if ( !curr_frame) {
   fprintf(stderr, "ERROR: frame is null... Exiting/n");
   //getchar();
   break;
  }
  // Do not release the frame!
  // Get frame size
  w = curr_frame->width;
  h = curr_frame->height;
  // Convert the frame image to grayscale
  if( ! gray_frame ) {
   //fprintf(stderr, "Allocate gray_frame/n");
   int channels = 1;
   gray_frame = cvCreateImage(
     cvGetSize(curr_frame),
     IPL_DEPTH_8U, channels);
  }
  cvCvtColor(curr_frame, gray_frame, CV_BGR2GRAY);
  
  // ==== Allocate memory for corner arrays ====
  if ( !eig_image) {
   //fprintf(stderr, "Allocate eig_image/n");
   eig_image = cvCreateImage(cvSize(w, h),
     IPL_DEPTH_32F, 1);
  }
  if ( !temp_image) {
   //fprintf(stderr, "Allocate temp_image/n");
   temp_image = cvCreateImage(cvSize(w, h),
     IPL_DEPTH_32F, 1);
  }
// Disable harris processing
//  if ( !harris_eig_image) {
//   //fprintf(stderr, "Allocate harris_eig_image/n");
//   harris_eig_image = cvCreateImage(cvSize(w, h),
//     IPL_DEPTH_32F, 1);
//  }
//  if ( !harris_temp_image) {
//   //fprintf(stderr, "Allocate harris_temp_image/n");
//   harris_temp_image = cvCreateImage(cvSize(w, h),
//     IPL_DEPTH_32F, 1);
//  }
  
  // ==== Corner Detection: MinEigenVal method ====
  start_timer();
  const int MAX_CORNERS = 100;
  CvPoint2D32f corners[MAX_CORNERS] = {0};
  int corner_count = MAX_CORNERS;
  double quality_level = 0.1;
  double min_distance = 5;
  int eig_block_size = 3;
  int use_harris = false;
  
  cvGoodFeaturesToTrack(gray_frame,
    eig_image,                    // output
    temp_image,
    corners,
    &corner_count,
    quality_level,
    min_distance,
    NULL,
    eig_block_size,
    use_harris);
  cvScale(eig_image, eig_image, 100, 0.00);
  eig_time = end_timer();
  cvShowImage(CORNER_EIG, eig_image);
  
// Disable harris processing
//  // ==== Corner Detection: Harris method ====
//  start_timer();
////  const int MAX_CORNERS = 100;
//  CvPoint2D32f harris_corners[MAX_CORNERS] = {0};
//  int harris_corner_count = MAX_CORNERS;
//  double harris_quality_level = 0.1;
//  double harris_min_distance = 1;
//  int harris_eig_block_size = 3;
//  int harris_use_harris = true;
//  
//  cvGoodFeaturesToTrack(gray_frame,
//    harris_eig_image,                    // output
//    harris_temp_image,
//    harris_corners,
//    &harris_corner_count,
//    harris_quality_level,
//    harris_min_distance,
//    NULL,
//    harris_eig_block_size,
//    harris_use_harris);
//  cvScale(harris_eig_image, harris_eig_image, 200, 0.50);
//  harris_time = end_timer();
//  cvShowImage(CORNER_HARRIS, harris_eig_image);
//  
//  fprintf(stderr, "harris time: %i  eig time: %i/n", harris_time, eig_time);
  
  // ==== Draw circles around detected corners in original image
  //fprintf(stderr, "corner[0] = (%f, %f)/n", corners[0].x, corners[0].y);
  for( int i = 0; i < corner_count; i++) {
   int radius = h/25;
   cvCircle(curr_frame,
     cvPoint((int)(corners[i].x + 0.5f),(int)(corners[i].y + 0.5f)),
     radius,
     target_color[0]);
  }
  cvShowImage(VIDEO_WINDOW, curr_frame);
  // If ESC key pressed, Key=0x10001B under OpenCV 0.9.7(linux version),
  // remove higher bits using AND operator
  if ( (cvWaitKey(10) & 255) == 27)
   break;
 }
 // Release the capture device housekeeping
 cvReleaseCapture( &capture);
 cvDestroyWindow(VIDEO_WINDOW);
 cvDestroyWindow(CORNER_EIG);
// Disable harris processing
// cvDestroyWindow(CORNER_HARRIS);
 return 0;
}