Resize items given absolute positions and sizes

Mark81

I read this page: https://doc.qt.io/qt-5/scalability.html but I still don't understand something that should be easy.
My QML root page is displayed into a QQuickWidget, with resizeMode == SizeRootObjectToView.
The root page contains an Image and its size is known - say 1920x1080.
This image is anchored to fill the parent, so it scale according to the main window.

Fine.
The issues rise when I have to add the other objects: images or text, mainly.
I receive a bitmap with their absolute positions and sizes referred to the original background image (1920x1080).

As you understand I need to scale everything in order to keep their correct appearance.
I thought it was simple:

property real ratio: root.width / 1920
property real img1_X: 330 // absolute position
property real img1_Y: 200

Image {
    x: img1_X * ratio
    y: img1_Y * ratio
    scale: ratio
}

but when I change the size of the viewport ratio doesn't change. It changes when I maximize or restore my QMainWindow but not when I resize it manually. Anyway, the images that are anchored to fill the root item are correctly resized every-time.

What am I missing here?

Mark81

I solved putting everything into an Itemand then applying the transformation needed:

property real ratio: imgBackground.paintedWidth / 1920.0
property real xBase: (root.width - imgBackground.paintedWidth) / 2.0
property real yBase: (root.height - imgBackground.paintedHeight) / 2.0

Item {
    x: 0; y: 0
    width: 1920
    height: 1080

    transform: [
        Scale { xScale: ratio; yScale: ratio},
        Translate { x: xBase; y: yBase }
    ]

    // objects with absolute position and size
}