I have an image which is 300x300. I set the ImageView fitWidth and fitHeight to 150x150, and by setting cache and smooth to true I get a perfectly smoothly scaled image. Now, if I place the image in a pane it shows up measuring 150x150 as expected, but if I place it on a button using setGraphic(Node) it shows up measuring 300x300. I think this is counter intuitive.

While it is possible to scale down the ImageView using setScaleX, Y, Z, that does not create a perfectly smoothly scaled image, so - at least in my use case - that is not a viable alternative.