Qgraphicsrectitem coordinate system on image resize

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QT

QT-Creator

OpenCV

resize

C++14

On an image(x by y), a QGraphicsRectItem is added, Let say Qrect(73, 77, 43, 28) Qrect(x,y,w,h). After resizing the image to 128 by 32, how this QGraphicsRectItem can be redrawn with proper co-ordinates.
The image is first resized, and then the graphicsRectItem to be added.
The grey area within the blue rectangle will be resized to 128 * 32, and then the red rectangle would be added on the resized image. How to get the co-ordinates of red rect on the resized image?
Image

What I have tried:

I tried few api in QGraphicsItem class, like maptoScene, maptoRect etc