How to get a snapshot of a video in Qt???

**stampede** · 28th July 2011, 17:05

With OpenCV its just few lines of code (for RGB24 images). This will extract frame number frameNo from video and convert to QImage:

Qt Code:

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QString pathToVideo = ...
CvCapture * capture = cvCaptureFromAVI( pathToVideo.toAscii(),constData() );
cvSetCaptureProperty(capture, CV_CAP_PROP_POS_FRAMES, frameNo);
IplImage * cvimg = cvQueryFrame(capture);
if(cvimg){ // this will be NULL if you specify invalid frame index
    QImage temp = QImage((const uchar*)cvimg->imageData,cvimg->width,cvimg->height,QImage::Format_RGB888);
    QImage image = temp.rgbSwapped(); // opencv images are BGR
}
cvReleaseCapture(&capture);

QString pathToVideo = ...
CvCapture * capture = cvCaptureFromAVI( pathToVideo.toAscii(),constData() );
cvSetCaptureProperty(capture, CV_CAP_PROP_POS_FRAMES, frameNo);
IplImage * cvimg = cvQueryFrame(capture);
if(cvimg){ // this will be NULL if you specify invalid frame index
    QImage temp = QImage((const uchar*)cvimg->imageData,cvimg->width,cvimg->height,QImage::Format_RGB888);
    QImage image = temp.rgbSwapped(); // opencv images are BGR
}
cvReleaseCapture(&capture);

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To work with other image formats, you will have to do some direct pixel manipulation.