[REG 5.3 -> 5.2.1] Bad icon resolution of .ico files

I've noticed that starting from QT 5.3.0, for some of our application icons, the image quality has become very poor. Given for example a MainWindow, try to set the attached icon as the windowIcon using Designer or the image of a menu item. What you can see is that the quality in the preview is very poor, even if the original image quality is good. Everything was fine with QT 5.2.1 and previous versions