Scale Factor in ZoomInteractor

Hi,

I am still developing my batik-based application and, while using the 
AbstractImageZoomInteractor, I came to the conclusion, that a function, 
that returns the current scale factor would be quite reasonable. I 
implemented it myself (yes, just copied your source) in my extended 
AbstractImageZoomInteractor:
        public double getZoomFactor() {
                int dy = yCurrent - yStart;
                if (dy < 0) {
                        dy = (dy > -5) ? 15 : dy - 10;
                } else {
                        dy = (dy < 5) ? 15 : dy + 10;
                }
                double s = dy / 15.0;
                s = (s > 0) ? s : -1 / s;
                return s;
        }
That is good enough for my application, as long as you will calculate 
the scaling factor the same way in future versions. As that can not be 
guaranteed, I would propose, you include the function in the class itself.
Please, feel free to tell me, if I have done some thinking mistakes or 
if I am too demanding.
Thank you very much and kind regards,

Tjorven