Show Qimage on graphicsView

jss193

Hello, Im trying to show a QImage into qgraphicsView, but it never works, I tried the following code:

   QGraphicsScene *scene = new QGraphicsScene;

    QImage image("path/QtImage.jpg");

    QGraphicsPixmapItem item(QPixmap::fromImage(image));

    scene->addItem(&item);

    ui->graphicsView->setScene(scene);

I fist create a scene,then trnasform the image into a Qpixmap item and add item to scene, then I set the scene into graphicsView. I can not see anything.

Can you help me please?

Christian Ehrlicher

@jss193 said in Show Qimage on graphicsView:

QGraphicsPixmapItem item(QPixmap::fromImage(image));

You're creating the object on the stack so it will get deleted once the function exits...

jss193

I created an object, why is it deleted? Dont understand well what you mean

Thank u

SGaist

Hi,

Here's an example:

void MyWidget::myFunction()
{
    QImage image("path/QtImage.jpg");
    QGraphicsPixmapItem item(QPixmap::fromImage(image));
} // << Here both image and item cease to exist.

jss193

Thank you, I know that but what I showed is not part of a function, is part of pushing a button, these are the actions inside that code, but it remanins not showing any image.

Thank you

Andy M

They are saying you should allocate the QGraphicsPixmapItem on the heap:

QGraphicsPixmapItem *item = new QGraphicsPixmapItem(QPixmap::fromImage(image));

The scene takes ownership of it:

https://doc.qt.io/qt-5/qgraphicsscene.html#addItem

SGaist

@jss193 said in Show Qimage on graphicsView:

Thank you, I know that but what I showed is not part of a function, is part of pushing a button, these are the actions inside that code, but it remanins not showing any image.

Thank you

A slot is still a function and the same logic applies to it as my shorten example.

Do as @Andy-M wrote and allocate the item on the heap.