convert QVideoFrame to QImage

问题

I want to get every frames from a QMediaPlayer and convert it to QImage (or cv::Mat)

so I used videoFrameProbed signal from QVideoProbe:

connect(&video_probe_, &QVideoProbe::videoFrameProbed, 
         [this](const QVideoFrame& currentFrame){
   //QImage img = ??
}

But I didn't find any way for getting QImage from QVideoFrame!

How can I convert QVideoFrame to QImage ?!

回答1:

You can use QImage's constructor:

 QImage img( currentFrame.bits(),
             currentFrame.width(),
             currentFrame.height(),
             currentFrame.bytesPerLine(),
             imageFormat);

Where you can get imageFormat from pixelFormat of the QVideoFrame:

 QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(currentFrame.pixelFormat());

回答2:

For QCamera output, that method doesn't always work. In particular, QVideoFrame::imageFormatFromPixelFormat() returns QImage::Format_Invalid when given QVideoFrame::Format_Jpeg, which is what's coming out of my QCamera. But this works:

QImage Camera::imageFromVideoFrame(const QVideoFrame& buffer) const
{
    QImage img;
    QVideoFrame frame(buffer);  // make a copy we can call map (non-const) on
    frame.map(QAbstractVideoBuffer::ReadOnly);
    QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(
                frame.pixelFormat());
    // BUT the frame.pixelFormat() is QVideoFrame::Format_Jpeg, and this is
    // mapped to QImage::Format_Invalid by
    // QVideoFrame::imageFormatFromPixelFormat
    if (imageFormat != QImage::Format_Invalid) {
        img = QImage(frame.bits(),
                     frame.width(),
                     frame.height(),
                     // frame.bytesPerLine(),
                     imageFormat);
    } else {
        // e.g. JPEG
        int nbytes = frame.mappedBytes();
        img = QImage::fromData(frame.bits(), nbytes);
    }
    frame.unmap();
    return img;
}

来源：https://stackoverflow.com/questions/27829830/convert-qvideoframe-to-qimage

标签

c++

qimage