Variable zoom speed

[www-chique]

I noticed that for really large images (more than 3000x3000), the zoom is too fast initially.
However, I could fix it by changing the delta / factor here:
updateScale(transform, transform.getScale() - delta / 10, e.offsetX, e.offsetY);
Tweaking that "10" or other values here solves the issue.
So I was thinking if it's possible to make it configurable as a property? Or somehow adjust it based on the image's dimension.

I am a newbie at this, so maybe someone else has a better way to implement this.