QGraphicsView: Images doesn't fit view frame

[janck]

I'm working on program which shows user some picture that is selected by him. But there is a problem because I would like to fit this picture in QGraphicsView's frame and the picture is really smaller than the frame.

So here's my code:

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
scn = new QGraphicsScene(this); // object defined in header
ui->graphicsView->setScene(scn);
scn->addPixmap(QPixmap::fromImage(*image));
ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
scn = new QGraphicsScene(this); // object defined in header
ui->graphicsView->setScene(scn);
scn->addPixmap(QPixmap::fromImage(*image));
ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

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I was trying a lot of solutions that I found on web, but no one didn't help me. The picture is in size around 40 x 60 px when the frame is 200 x 400 px. What could be wrong?

[wysota]

How does the result you get differ from what you expect?

[janck]

Here is the picture of current state and what I want:
USRlisR.png

[wysota]

What does scn->itemsBoundingRect() return?

[karankumar1609]

You have not set the sceneRect for QGraphicsScene....

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
    scn = new QGraphicsScene(this); // object defined in header
    // scn->setSceneRect(ui->graphicsView->Rect()); // SOMETHING LIHE THIS
    ui->graphicsView->setScene(scn);
    scn->addPixmap(QPixmap::fromImage(*image));
    ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
    scn = new QGraphicsScene(this); // object defined in header
    // scn->setSceneRect(ui->graphicsView->Rect()); // SOMETHING LIHE THIS
    ui->graphicsView->setScene(scn);
    scn->addPixmap(QPixmap::fromImage(*image));
    ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

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[janck]

What does scn->itemsBoundingRect() return?

QRectF(0,0 1078x1922)

You have not set the sceneRect for QGraphicsScene....

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
    scn = new QGraphicsScene(this); // object defined in header
    // scn->setSceneRect(ui->graphicsView->Rect()); // SOMETHING LIHE THIS
    ui->graphicsView->setScene(scn);
    scn->addPixmap(QPixmap::fromImage(*image));
    ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

image = new QImage(data.absoluteFilePath()); // variable data is defined when calling this method and object image is defined as QImage in header
    scn = new QGraphicsScene(this); // object defined in header
    // scn->setSceneRect(ui->graphicsView->Rect()); // SOMETHING LIHE THIS
    ui->graphicsView->setScene(scn);
    scn->addPixmap(QPixmap::fromImage(*image));
    ui->graphicsView->fitInView(scn->itemsBoundingRect(),Qt::KeepAspectRatio);

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It's same as before.

[wysota]

QRectF(0,0 1078x1922)

And how large is your view's viewport?

[janck]

Output from ui->graphicsView->viewport->size() is QSize(98, 28) and the frame is about 200 x 400 px.

[karankumar1609]

You were trying to add an image in background of QGraphicsView
Try to add background image of QGraphicsView, or QGraphicsScene.

try:

ui->graphicsView->setBackgroundBrush(QBrush(*image));
// set scene background transparent. ;)

ui->graphicsView->setBackgroundBrush(QBrush(*image));
// set scene background transparent. ;)

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OR

ui->graphicsView->fitInView(scn->sceneRect(), Qt::KeepAspectRatio);

ui->graphicsView->fitInView(scn->sceneRect(), Qt::KeepAspectRatio);

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ALL I CAN SE IS THE PROBLEM OF SCENE RECT.

[janck]

None of that helped me, but I've changed fitInView's KeepAspectRatio to

ui->graphicsView->fitInView(scn->sceneRect(),Qt::KeepAspectRatioByExpanding);

ui->graphicsView->fitInView(scn->sceneRect(),Qt::KeepAspectRatioByExpanding);

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Image is now little bigger than before, but that is not solution. Is there any other way to insert image into dialog's form, so I can apply images with all aspect ratios and there wouldn't be visible border?

[wysota]

Output from ui->graphicsView->viewport->size() is QSize(98, 28) and the frame is about 200 x 400 px.

If you are trying to call fitInView() before the view is first shown then this will not work. The view only gets a real size when it is first shown. You can either reimplement showEvent() or use a singleshot timer or QMetaObject::invokeMethod() to delay calling fitInView.

[janck]

It seems that there is no solution for QGraphicsView. I'm looking at QLabel which also provides support for QPixmap and looks it's easier to show image in here. What would be the command for fitting image into QLabel, because scaledContents only scale image, so it doesn't keep ratio?

[wysota]

There is no equivalent. You can implement a custom widget that does what you want or use QGraphicsView. I assure you the latter works, I've used in many times like that. However implementing a custom widget is very easy.

[janck]

I found another code on web and adjusted it to my project, but it's same as before. I really don't know what could be wrong and as well I don't understand you last tips - probably because I'm into Qt only few weeks. Here is my current code:

image = new QImage(filePath);
scn = new QGraphicsScene(this);
ui->graphicsView->setScene(scn);
scn->addPixmap(QPixmap::fromImage(*image));
scn->setSceneRect(0,0,image->width(),image->height());
ui->graphicsView->fitInView(scn->sceneRect(),Qt::KeepAspectRatioByExpanding);

image = new QImage(filePath);
scn = new QGraphicsScene(this);
ui->graphicsView->setScene(scn);
scn->addPixmap(QPixmap::fromImage(*image));
scn->setSceneRect(0,0,image->width(),image->height());
ui->graphicsView->fitInView(scn->sceneRect(),Qt::KeepAspectRatioByExpanding);

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What can I do to fit image into this frame?

Thank you very much!

[wysota]

I already told you -- you cannot call fitInView() before the view is first shown because it has no size yet. You can find as many "codes on web" but they will all fail because of the same reason. You need to do as I told you -- call fitInView() when the view is already visible.

[janck]

Ok, I see what's the problem. But how can I do that image would fit the frame on setup of dialog?

[wysota]

Am I wasting my time here? Did you read post #11? You have two possible solutions there. And in #13 there is a suggestion to implement a custom widget that draws a resized pixmap. It's as easy as subclassing QWidget, reimplementing its paintEvent() and calling QPainter::drawPixmap().

[janck]

Sorry, I didn't know that showEvent() also exists for Dialogs. This solved my problem, so thank you!