Set of Qt / OpenCV snippets

cvutils.cpp

/*
 * Convert a cv::Mat frame to a QPixmap and show it in a Qt object.
 *
 * Parameters
 * ----------
 *     frame : cv::Mat
 *         Input image in BGR format.
 */
void updateImageFrameToQLabel(cv::Mat& frame)
{
    // prepare frame data
    cv::cvtColor(frame, frame, cv::COLOR_BGR2RGB);
    // convert to pixmap
    QImage image = QImage(frame.data, frame.cols, frame.rows, frame.step, QImage::Format_RGB888);
    QPixmap pixmap = QPixmap::fromImage(image);
    // update label content
    ui->image_frame_label->setPixmap(pixmap); // no resize
}

void updateImageFrameToQGraphicsView(cv::Mat& frame)
{
    // prepare frame data
    cv::cvtColor(frame, frame, cv::COLOR_BGR2RGB);
    // convert to pixmap
    QImage image = QImage(frame.data, frame.cols, frame.rows, frame.step, QImage::Format_RGB888);
    QPixmap pixmap = QPixmap::fromImage(image);
    // update graphics view content
    // parent : QWidget*
    // m_p_scene = new QGraphicsScene(parent)
    // m_p_scene_pixmap = m_p_scene->addPixmap(QPixmap());
    // ui->graphicsView->setScene(m_p_scene);
    m_p_scene_pixmap->setPixmap(pixmap);
    m_p_scene->setSceneRect(0, 0, pixmap.width(), pixmap.height());
    ui->graphicsView->fitInView(m_p_scene->sceneRect(), Qt::KeepAspectRatio); // auto-resize
}