Getting coordinates of all QGraphicsItem s on a QGraphicsScene

**xd123** · 19th April 2020, 17:50

Hi, I'm developing a GUI application in Qt where a user can annotate a selected image with various shapes of QGraphicsItem, for example QGraphicsRectItem, QGraphicsPolygonItem, and so on. Each of my shapes has a distinct button for adding the shape like so:

Qt Code:

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void MainWindow::on_pushButton_11_clicked()  // rectangle shape creator
{
    QGraphicsRectItem* rectItem = new QGraphicsRectItem(QRectF(0, 0, 320, 240));
    QColor brush_color(Qt::blue); //fill color
    brush_color.setAlpha(50); // alpha index makes brush color more opaque
    QPen blackpen(Qt::black); //border color
    blackpen.setWidth(2); // border width
    rectItem->setBrush(brush_color); // using brush color
    rectItem->setPen(blackpen);
    rectItem->setFlag(QGraphicsItem::ItemIsMovable); // making the object dragable across graphics view
    scene->addItem(rectItem);
}

void MainWindow::on_pushButton_11_clicked()  // rectangle shape creator
{
    QGraphicsRectItem* rectItem = new QGraphicsRectItem(QRectF(0, 0, 320, 240));
    QColor brush_color(Qt::blue); //fill color
    brush_color.setAlpha(50); // alpha index makes brush color more opaque
    QPen blackpen(Qt::black); //border color
    blackpen.setWidth(2); // border width
    rectItem->setBrush(brush_color); // using brush color
    rectItem->setPen(blackpen);
    rectItem->setFlag(QGraphicsItem::ItemIsMovable); // making the object dragable across graphics view
    scene->addItem(rectItem);
}

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Whenever the user presses a shape button the shape is created in the center of the scene and can be then moved. What I am looking to do now is to retrieve all graphics items on the scene and their respective coordinates to a text file so that when the user is done, (s)he can save the work and load the annotation shapes at the same coordinates next time.

So far I have done the most progress with QList<QGraphicsItem*> graphicsItemList = scene->items() which enables me to get all the items, but strangely enough I don't know if the output I'm getting is correct as for example with 3 shapes (Rectangle, Ellipse and a Triangle) I get this output to my console from graphicsItemList:
qt output.jpg

In case that this is the correct and expected output my question would be, how would I write down all this information into a text file so that Qt could re-create these shapes at the given coordinates?

My format for the text file would be that each line represents a shape(with for example a number, 1 being rectangle, 2 ellipse and so on) followed by its coordinates like so:
1 0.3095703125 0.6815519765739385 0.359375 0.4260614934114202

At least that is the format that makes the most sense in my head, any suggestions, questions and potential fixes are welcome, thanks.