Display QImage within main window

Question

I'm trying to display an image with Qt, I can get it to appear in a separate window, but I can't make it appear within the main window

Qt_first w;
w.show();

This shows the window I designed in Qt designer, how do I access the Qlabel(Image_Lbel) I put within the QWidget (centralWidget) of that window?

I generated a stripy image that shows correctly, just not within the correct window

QSize size = QSize(640,480);
QImage::Format format = QImage::Format_ARGB32;
QImage image = QImage::QImage(size, format);
//generate
QLabel myLabel;
myLabel.setPixmap(QPixmap::fromImage(image));
myLabel.show();

I get the feeling it could be I haven't included the files from the creator or the namespaces any suggestion much appreciated

Answer 1

I guess your Label is getting displayed independently. Set the parent of label to your main window. Then your Label will displayed inside your main window.

So use,

QLabel *myLabel = new QLabel(this); // sets parent of label to main window 
myLabel->setPixmap(QPixmap::fromImage(image));
myLabel->show();

You can also use move function for moving your label within the main window.

Answer 2

If you want to set the label from outside the Qt_first class, you need to add a method to do this. For example (in qt_first.cpp, change qt_first.h accordingly):

void Qt_first::setImageLabel(const QImage& image)
{
    ui->Image_Lble.setPixmap(QPixmap::fromImage(image));
}

ui in this example is the object that represents the UI that you created with Qt Designer.

Answer 3

I used a combination of both answers, thanks to both

Qt_first w;  // the UI I made with Qt creator
QLabel *myLabel = w.getImageLabel();
myLabel->setPixmap(QPixmap::fromImage(image));
w.show();

With the following inside the Qt_first class

QLabel* Qt_first::getImageLabel(){  
    QLabel *myLabel = ui.Image_Label;
    return myLabel;
}