> Hello, > > I need a tipp for drawing an oval around a dynamic textfield with > variable line numbers and variable width? Perhaps, someone can point > me to a good tutorial dealing with such geometry questions. > The drawOval methods I am using have width and height as parameters, > but of course I can't use width and height of the textfield without a > padding. How can I calculate an i appropriate padding?
Hi, Assuming your bezier curve is at least an approximate ellipse (I haven't done the maths to be sure), here's how you can find an ellipse that contains a particular rectangle. Suppose the rectangle has half-width w and half-height h. You want an ellipse of half-width a and half-height b such that the point (w,h) lies on it (assume it's centred on (0,0): you can add the x,y coordinates at the end). The locus of a point P on an ellipse aligned with the axes is: P = (a * cos(t), b * sin(t)), where t lies between 0 and 2*pi (we only need to think about t between 0 and pi/2, though). So we need to find a and b such that a*cos(t) = w and b*sin(t) = h, for some t. Notice that since we've got three variables and two equations, there are an infinite number of possible solutions. If you pick any value of t between 0 and pi/2, you can simply read off the values of a and b as a = w/cos(t), b = h/sin(t). So the only tricky bit is choosing a value of t that makes your ellipse fit the rectangle reasonably tightly. I think I'd do it ideally by trying to minimise the value of (a-w)^2 + (b-h)^2, thus minimising the distance of the extremes from the rectangle edges, but that's a bit ugly. In practice, I think you could do it by choosing t based on the ratio w/h (try w*(pi/4)/h if w<h, pi/4 + h*(pi/4)/w if w>h as a first thought, but I haven't tried it) HTH Danny _______________________________________________ Flashcoders@chattyfig.figleaf.com To change your subscription options or search the archive: http://chattyfig.figleaf.com/mailman/listinfo/flashcoders Brought to you by Fig Leaf Software Premier Authorized Adobe Consulting and Training http://www.figleaf.com http://training.figleaf.com
