opencv怎么截取视频图片

double currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
std::cout << "CV_CAP_PROP_POS_FRAMES = " << currentPos << std::endl;

// position_slider 0 - 100
double noFrame = position_slider*nbFrames / 100;

// solution 1
bool success = capture.set(CV_CAP_PROP_POS_FRAMES, noFrame);
// solution 2
double frameRate = capture.get(CV_CAP_PROP_FPS);
double frameTime = 1000.0 * noFrame / frameRate;
bool success = capture.set(CV_CAP_PROP_POS_MSEC, frameTime);

if (!success) {
std::cout << "Cannot set frame position from video file at " << noFrame << std::endl;
return;
}

currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
if (currentPos != noFrame) {
std::cout << "Requesting frame " << noFrame << " but current position == " << currentPos << std::endl;
}

success = capture.read(frame_aux);
if (!success) {
std::cout << "Cannot get frame from video file " << std::endl;
return;
}
imshow("test", frame_aux);