add a fixed image height and width text field

Issue Summary

Max and fixed "width" refers to the rendered text width, so when rotated, it's the "image height". There is no way to say, "I want this resultant image to be exactly x-width or y-height."

I am on the pursuit of a book-like interface for primary menu of book spines and active item of book face, and to allow for pairing of book spine/binding (side) with book face/front, the image heights need to match across presets. Having the ability to set the preset of book_side to one image height and the book_front to be set to the same image height would lick it, I think.