OpenCV学习之滚动条播放视频

#include <stdio.h>
#include <iostream>
#include <fstream>
#include "cv.h"
#include "highgui.h"
//滚动条播放视频
int g_slider_position = 0;
CvCapture* g_capture = NULL;
void onTrackbarSlide(int pos) {
    cvSetCaptureProperty(
        g_capture,
        CV_CAP_PROP_POS_FRAMES,
        //CV_CAP_PROP_POS_FRAMES以帧数来设置读入位置
        //CV_CAP_PROP_POS_AVI_RATIO以视频长度比例来设置读入位置
        pos
    );
}
int main(int argc, char** argv) {
    cvNamedWindow("Example", CV_WINDOW_AUTOSIZE);
    g_capture = cvCreateFileCapture("沙画.mp4");
    int frames = (int)cvGetCaptureProperty(
        g_capture,
        CV_CAP_PROP_FRAME_COUNT 
        //获取总帧数
    );
    if (frames != 0) {
        //有些编码方式帧数获取不到，只能直接播放视频，看不到滚动条
        cvCreateTrackbar(
            "Positon",
            "Example",
            &g_slider_position,
            frames,
            onTrackbarSlide
        );
        IplImage* frame;
        while (1) {
            frame = cvQueryFrame(g_capture);
            if (!frame) break;
            cvShowImage("Example", frame);
            //停顿33ms,可以通过cvcapturefromcamera返回的cvcapture准确的确定帧率
            char c = cvWaitKey(33);
            if (c == 27) break;//ASCII码esc键
        }
        cvReleaseCapture(&g_capture);
        cvDestroyWindow("Example");
        return(0);
    }
}