Qt + OpenCV - Displaying images on QLabel

Question

I'm trying to capture live view from camera, and redirecting it to show up on QLabel. But only half view comes (see below):

The left hand side window, is shown using cv::imshow(), which works perfectly. I'm capturing the Mat in a different thread, and then emitting a signal with a Qimage as a parameter, and then setting the image to the QLabel in the slot.

here's the code:

while(true){
    cam >> mat;
    cv::imshow("name",mat);
    emit send_UIupdate(mat2qimage(mat));
}

and in the slot setting the image to Qlabel:

void Dialog::updateUI(const QImage &img){
    label->setPixmap(QPixmap::fromImage(img));
}

using the below to convert Mat to QImage:

QImage camera::mat2qimage(const cv::Mat& mat) {
    cv::Mat rgb;
    cv::cvtColor(mat, rgb, CV_BGR2RGB);
    return QImage((const unsigned char*)(rgb.data), rgb.cols, rgb.rows, QImage::Format_RGB888);
}

Any suggestions, to solve this problem ??

Solution 1

you can try this :

QImage MainWindow::putImage(const Mat& mat)
{
    // 8-bits unsigned, NO. OF CHANNELS=1
    if(mat.type()==CV_8UC1)
    {
        // Set the color table (used to translate colour indexes to qRgb values)
        QVector<QRgb> colorTable;
        for (int i=0; i<256; i++)
            colorTable.push_back(qRgb(i,i,i));
        // Copy input Mat
        const uchar *qImageBuffer = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage img(qImageBuffer, mat.cols, mat.rows, mat.step, QImage::Format_Indexed8);
        img.setColorTable(colorTable);
        return img;
    }
    // 8-bits unsigned, NO. OF CHANNELS=3
    if(mat.type()==CV_8UC3)
    {
        // Copy input Mat
        const uchar *qImageBuffer = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage img(qImageBuffer, mat.cols, mat.rows, mat.step, QImage::Format_RGB888);
        return img.rgbSwapped();
    }
    else
    {
        qDebug() << "ERROR: Mat could not be converted to QImage.";
        return QImage();
    }
}

I call it with a QTimer. I got it from there : http://code.google.com/p/qt-opencv-multithreaded/

Hope this help.

Solution 2

VideoCapture cap("video.avi");
Mat frame;
QImage img;
QPixmap pixel;
while(cap.isOpened())
{
    cap >> frame;
    img= QImage((uchar*) frame.data, frame.cols, frame.rows, frame2.step, QImage::Format_RGB888);
    pixel = QPixmap::fromImage(img);
    ui->label->setPixmap(pixel);
}