Spline.java

package Charts;

import java.util.ArrayList;
import java.util.List;

public class Spline {

    public SplinePoint[] copyPoints() {
        SplinePoint[] ps = new SplinePoint[points.length];
        for (int i = 0; i < ps.length; i++) {
            ps[i] = new SplinePoint(points[i].getX(), points[i].getY());
        }
        return ps;
    }

    public SplinePoint[] getPoints() {
        return points;
    }

    public void setPoints(SplinePoint[] points) {
        this.points = points;
    }

    private SplinePoint[] points;

    public Spline() {
    }

    public List<SplinePoint> createSpline(float f, SplinePoint... point) {
        this.points = point;
        List<SplinePoint> list = new ArrayList<>();
        for (float t = 0f; t < (float) (point.length - 3.0f) * f; t += 0.01f) {
            list.add(getSpline(t));
        }
        return list;
    }

    public SplinePoint getSpline(float t) {
        int p0, p1, p2, p3;
        p1 = (int) t + 1;
        p2 = p1 + 1;
        p3 = p2 + 1;
        p0 = p1 - 1;
        t = t - (int) t;
        float tt = t * t;
        float ttt = tt * t;
        float q1 = -ttt + 2.0f * tt - t;
        float q2 = 3.0f * ttt - 5.0f * tt + 2.0f;
        float q3 = -3.0f * ttt + 4.0f * tt + t;
        float q4 = ttt - tt;
        double tx = 0.5f * (points[p0].getX() * q1 + points[p1].getX() * q2 + points[p2].getX() * q3 + points[p3].getX() * q4);
        double ty = 0.5f * (points[p0].getY() * q1 + points[p1].getY() * q2 + points[p2].getY() * q3 + points[p3].getY() * q4);
        return new SplinePoint(tx, ty);
    }
}