internal/restorable/image.go
func (i *Image) internalSize() (int, int) {
	if i.w2 == 0 || i.h2 == 0 {
		w, h := i.image.Size()
		i.w2 = graphics.InternalImageSize(w)
		i.h2 = graphics.InternalImageSize(h)
	}
	return i.w2, i.h2
}
func (i *Image) internalSize() (int, int) {
	if i.w2 == 0 || i.h2 == 0 {
		w, h := i.image.Size()
		i.w2 = graphics.InternalImageSize(w)
		i.h2 = graphics.InternalImageSize(h)
	}
	return i.w2, i.h2
}
// internalSize returns the size of the internal texture.