//
// example 8-2
//
//
//


#include <cv.h>
#include <highgui.h>

IplImage* g_image = NULL;
IplImage* g_gray = NULL;
int g_thresh = 100;
CvMemStorage* g_storage = NULL;

void on_trackbar(int) {
 if( g_storage==NULL ) {
 g_gray = cvCreateImage( cvGetSize(g_image), 8, 1 );
 g_storage = cvCreateMemStorage(0);
 } else {
 cvClearMemStorage( g_storage );
 }
 CvSeq* contours = 0;
 cvCvtColor( g_image, g_gray, CV_BGR2GRAY );
 cvThreshold( g_gray, g_gray, g_thresh, 255, CV_THRESH_BINARY );
 cvFindContours( g_gray, g_storage, &contours );
 cvZero( g_gray );
 if( contours )
 cvDrawContours( 
 g_gray, 
 contours, 
 cvScalarAll(255),
 cvScalarAll(255), 
 100 
 );
 cvShowImage( "Contours", g_gray );
}

int main( int argc, char** argv )
{
 if( argc != 2 || !(g_image = cvLoadImage(argv[1])) )
 return -1;
 cvNamedWindow( "Contours", 1 );
 cvCreateTrackbar( 
 "Threshold", 
 "Contours", 
 &g_thresh, 
 255, 
 on_trackbar
 );
 on_trackbar(0);
 cvWaitKey();
 return 0; 
}