Display video using QImage in the same window? - qt

Question

I am trying to display the video taken by a simulator. I am implementing the QT code in ROS by including its header file. My code is running.
PROBLEM:: Everytime the new window is opened to display the frame. I have kept cvWaitKey(10000) so that new windows will come after a time delay. But the updated frames should come inside the same window. Pls suggest how can i do it?? My code is following:
void imageCallback( const sensor_msgs::ImageConstPtr& msg) //const sensor_msgs::ImageConstPtr&
{
imagePublisher.publish (cv_ptr->toImageMsg());
QImage temp(&(msg->data[0]), msg->width, msg->height, QImage::Format_RGB888);
QImage image;
image=temp;
// QT Layout with button and image
static QWidget *window = new QWidget;
static QLabel *imageLabel= new QLabel;
static QPushButton* quitButton= new QPushButton("Quit");
static QPushButton* exitButton= new QPushButton("Exit Image");
QVBoxLayout* layout= new QVBoxLayout;
imageLabel->setPixmap(QPixmap::fromImage(image));
layout->addWidget(imageLabel);
layout->addWidget(exitButton);
layout->addWidget(quitButton);
window->setLayout(layout);
QObject::connect(quitButton, SIGNAL(clicked()),window, SLOT(close())); // Adding Buttons
QObject::connect(exitButton, SIGNAL(clicked()),imageLabel, SLOT(close()));
window->show();
cvWaitKey(1);
}
int main(int argc, char **argv)
{
ros::init(argc, argv, "imageSelectNode");
ros::NodeHandle n("~");
image_transport::ImageTransport it(n);
image_transport::Subscriber sub = it.subscribe("/camera/image_raw",1, imageCallback);
imagePublisher = it.advertise("imagePublisherTopic", 1); //Publish the image in 'imagePublisherTopic' node
QApplication a(argc, argv);
ros::spin();
return 0;
}

Answer 1

A new window is opened, because you create a new QLabel on each frame. What you need is - one QLabel, which pixmap you should change. The simplest way to do that is to make your imageLabel static:
static QLabel *imageLabel = new QLabel;
Update:
If you want to do some manipulations to this label once (like adding it to a layout), you could do something like this:
QLabel * createLabel()
{
QLabel *l = new QLabel;
layout->addWidget(l);
return l;
}
...
static QLabel *imageLabel = createLabel();
Update 4:
QLabel * createLabel()
{
QWidget *window = new QWidget;
QLabel *imageLabel= new QLabel;
QPushButton* quitButton= new QPushButton("Quit");
QPushButton* exitButton= new QPushButton("Exit Image");
QVBoxLayout* layout= new QVBoxLayout;
layout->addWidget(imageLabel);
layout->addWidget(exitButton);
layout->addWidget(quitButton);
window->setLayout(layout);
QObject::connect(quitButton, SIGNAL(clicked()),window, SLOT(close()));
QObject::connect(exitButton, SIGNAL(clicked()),imageLabel, SLOT(close()));
window->show();
return imageLabel;
}
void imageCallback( const sensor_msgs::ImageConstPtr& msg)
{
imagePublisher.publish (cv_ptr->toImageMsg());
QImage temp(&(msg->data[0]), msg->width, msg->height, QImage::Format_RGB888);
QImage image;
image = temp;
static QLabel *imageLabel = createLabel();
imageLabel->setPixmap(QPixmap::fromImage(image));
cvWaitKey(1);
}