Add an Image to certain position in QGraphicsScene

Question

I am developing a program to allow users to select a file and add it to QGraphicsView. Everything esle works fine except item-positioning. All images are displayed in the same position. Source code is as below

//user action to add an image
    void MainWindow::on_actionMessage_triggered()
    {
        const int width = 150;
        const int height = 200;

        QString fileName = QFileDialog::getOpenFileName(this,"Open Image File",QDir::currentPath());

            QImage image(fileName);
            QGraphicsPixmapItem* item = new QGraphicsPixmapItem(QPixmap::fromImage(image));
            item->setScale(0.1);
            item->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable);
            item->setPos(scene->items.count()*width,scene->items.count()*height);
            scene->addItem(item);
    }


//initialize Scene
    MainWindow::MainWindow(QWidget *parent) :  QMainWindow(parent), ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
        this->setBaseSize(800, 600);

        scene = new QGraphicsScene(0,0,600,400);
        scene->setSceneRect(0,0,600,400);

        ui->graphicsView->setScene(scene);
        //ui->graphicsView->fitInView(scene.sceneRect());
        ui->graphicsView->show();
    }

`scene->items.count()` is not valid. It should be `scene->items().count()`. Is it so in your real code? — Pavel Strakhov, Jul 05 '13 at 05:55
What do you mean by "the same"? `scene->items.count()` doesn't compile! How could you not notice that? I've run your code, it works fine to me. I think there is an issue with your build system (e.g. the project doesn't compile before running). — Pavel Strakhov, Jul 06 '13 at 07:38
Have you checked the values that are getting passed in to setpos? — TheDarkKnight, Jul 06 '13 at 10:09
Yes it is a bug in the code. The values setPos were wrong.Thank you guys for your help! — Dustin Sun, Jul 06 '13 at 16:19
I shared the working code here. https://stackoverflow.com/a/45280054/1999190 — Shachi, Jul 24 '17 at 12:01

score 1 · Answer 1 · answered Jul 05 '13 at 07:59

1

When using the QGraphicsSystem you need to think about which coordinate system you're affecting when setting and retrieving an item's position.

In this case of an an item that has no parent and while the Qt docs states that with no parent it will set the scene coordinates of the item, it would require knowledge of the scene to do that as you're expecting.

Therefore, add the item to the scene before calling setPos.

answered Jul 05 '13 at 07:59

TheDarkKnight

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Using `setPos` before `addItem` works fine. Qt docs are indeed not clear about it, but it seems that item position is stored in the item object and applied to it when it's added to a scene. – Pavel Strakhov Jul 06 '13 at 07:21
I've had problems in the past with setting the position first, but maybe that has since been fixed. I'll have a think about the problem a bit more. – TheDarkKnight Jul 06 '13 at 10:05

score 1 · Answer 2 · answered Jul 24 '17 at 12:04

1

I shared the working code here.

https://stackoverflow.com/a/45280054/1999190

Also,if you want the default position at top, instead of center,simply change the alignment of graphicsView.

 ui->graphicsView->setAlignment( Qt::AlignLeft | Qt::AlignTop );

answered Jul 24 '17 at 12:04

Shachi

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score 0 · Answer 3 · answered Aug 17 '16 at 02:44

0

try to use mapToscene function. ex: mapToscene(Position Coordinates) it will definitely work.

answered Aug 17 '16 at 02:44

Vishal Karathiya

1

Add an Image to certain position in QGraphicsScene

3 Answers3