nearest point on line

    public static Point2D nearestPointOnLine(double ax, double ay, double bx, double by, double px, double py,
            boolean clampToSegment, Point2D dest) {
        // Thanks StackOverflow!
        // http://stackoverflow.com/questions/1459368/snap-point-to-a-line-java
        if (dest == null) {
            dest = new Point2D.Double();
        }

        double apx = px - ax;
        double apy = py - ay;
        double abx = bx - ax;
        double aby = by - ay;

        double ab2 = abx * abx + aby * aby;
        double ap_ab = apx * abx + apy * aby;
        double t = ap_ab / ab2;
        if (clampToSegment) {
            if (t < 0) {
                t = 0;
            } else if (t > 1) {
                t = 1;
            }
        }
        dest.setLocation(ax + abx * t, ay + aby * t);
        return dest;
    }