OpenCV学习——用Trackbar模仿一个按钮

// An example program in which the
// user can draw boxes on the screen.
//
#include <cv.h>
#include <highgui.h>
#include <stdio.h>
/* License:
Oct. 3, 2008
Right to use this code in any way you want without warrenty, support or any guarentee of it working.

BOOK: It would be nice if you cited it:
Learning OpenCV: Computer Vision with the OpenCV Library
by Gary Bradski and Adrian Kaehler
Published by O'Reilly Media, October 3, 2008

AVAILABLE AT:
http://www.amazon.com/Learning-OpenCV-Computer-Vision-Library/dp/0596516134
Or: http://oreilly.com/catalog/9780596516130/
ISBN-10: 0596516134 or: ISBN-13: 978-0596516130

OTHER OPENCV SITES:
* The source code is on sourceforge at:
http://sourceforge.net/projects/opencvlibrary/
* The OpenCV wiki page (As of Oct 1, 2008 this is down for changing over servers, but should come back):
http://opencvlibrary.sourceforge.net/
* An active user group is at:
http://tech.groups.yahoo.com/group/OpenCV/
* The minutes of weekly OpenCV development meetings are at:
http://pr.willowgarage.com/wiki/OpenCV
*/
//
// Using a trackbar to create a "switch" that the user can turn on and off.
// We make this value global so everyone can see it.
//
int g_switch_value = 1;
void switch_off_function() {printf("Pause\n");}; //YOU COULD DO SOMETHING WITH THESE FUNCTIONS TOO
void switch_on_function() {printf("Run\n");};

//
// This will be the callback that we give to the
// trackbar.
//
void switch_callback( int position ) {
if( position == 0 ) {
switch_off_function();
} else {
switch_on_function();
}
}

//OK, OK, I ADDED READING A MOVIE AND USING THE "BUTTON" TO STOP AND GO
int main( int argc, char* argv[] ) {
IplImage *frame; //To hold movie images
CvCapture* g_capture = NULL;
if((argc < 2 )|| !(g_capture = cvCreateFileCapture( argv[1] ))){
printf("Failed to open %s\n",argv[1]);
return -1;
}

// Name the main window
//
cvNamedWindow( "Example4_2", 1 );

// Create the trackbar. We give it a name,
// and tell it the name of the parent window.
//
cvCreateTrackbar(
"Switch",
"Example4_2",
&g_switch_value,
1,
switch_callback
);

// This will just cause OpenCV to idle until
// someone hits the "Escape" key.
//
while( 1 ) {
if(g_switch_value){
frame = cvQueryFrame( g_capture );
if( !frame ) break;
}
cvShowImage( "Example4_2", frame);
if(cvWaitKey(10)==27 ) break;
}

//CLEAN UP
cvReleaseCapture( &g_capture );
cvDestroyWindow( "Example4_2" );
return(0);

}