opencv_study第三篇|视频播放控制

#include <stdio.h>
#include <iostream>
#include <fstream>
#include "cv.h"
#include "highgui.h"
using namespace std;
int        g_slider_position = 0;
CvCapture* g_capture = NULL;
void onTrackbarSlide(int pos) 
{
	cvSetCaptureProperty(g_capture,CV_CAP_PROP_POS_FRAMES,pos);
}

//Hack because sometimes the number of frames in a video is not accessible. 
//Probably delete this on Widows
int getAVIFrames(char * fname) {
	char tempSize[4];
	// Trying to open the video file
	ifstream  videoFile(fname, ios::in | ios::binary);
	// Checking the availablity of the file
	if (!videoFile) {
		cout << "Couldn’t open the input file " << fname << endl;
		exit(1);
	}
	// get the number of frames
	videoFile.seekg(0x30, ios::beg);
	videoFile.read(tempSize, 4);
	int frames = (unsigned char)tempSize[0] + 0x100 * (unsigned char)tempSize[1] + 0x10000 * (unsigned char)tempSize[2] + 0x1000000 * (unsigned char)tempSize[3];
	videoFile.close();
	return frames;
}


int main(int argc, char **argv) 
{
	cvNamedWindow("Example2_3", CV_WINDOW_AUTOSIZE);
	g_capture = cvCreateFileCapture("test.avi");
	IplImage *foo = cvQueryFrame(g_capture);


	int frames = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FRAME_COUNT);

	int tmpw = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FRAME_WIDTH);

	int tmph = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FRAME_HEIGHT);

	printf("opencv frames %d w %d h %d\n", frames, tmpw, tmph);

	frames = getAVIFrames("test.avi"); //This is a hack because on linux, getting number of frames often doesn't work

	printf("hacked frames %d w %d h %d\n", frames, tmpw, tmph);

	cvCreateTrackbar("Position","Example2_3",&g_slider_position,frames,onTrackbarSlide);
	IplImage* frame;
	frames = 0;
	while (1)
	{
		frame = cvQueryFrame(g_capture);
		if (!frame) 
			break;
		//      int frames = cvGetCaptureProperty( g_capture, CV_CAP_PROP_POS_FRAMES);//This should work, sometimes it does not on linux
		frames++; //My cheat
		printf("\nFrame number=%d\n", frames);
		cvSetTrackbarPos("Position", "Example2_3", frames);
		cvShowImage("Example2_3", frame);
		char c = (char)cvWaitKey(10);
		if (c == 27) 
			break;
	}
	cvReleaseCapture(&g_capture);
	cvDestroyWindow("Example2_3");
	return(0);
}