Java 绘制平滑曲线

Java 中可以使用 GeneralPath::cubicTo() 函数绘制如下的平滑曲线

绘制平滑曲线的关键是控制点的计算,sp 为线段的起始点,ep 为线段的终点,c1,c2 为贝塞尔曲线的控制点,其坐标计算如下

下面就用个简单的程序介绍怎么绘制平滑曲线,主要部分为 for 循环里控制点 c1, c2 的计算,注意不能把它们的顺序弄反了哦,否则生成的曲线很奇怪的。

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import javax.swing.*;
import java.awt.*;
import java.awt.geom.GeneralPath;
public class DrawSmoothCurve extends JPanel {
private Point[] points = {
new Point(0, 0),
new Point(100, 100),
new Point(200, -100),
new Point(300, 100),
new Point(330, -80),
new Point(350, -70)
};
GeneralPath path = new GeneralPath();
public DrawSmoothCurve() {
path.moveTo(points[0].x, points[0].y);
for (int i = 0; i < points.length-1; ++i) {
Point sp = points[i];
Point ep = points[i+1];
Point c1 = new Point((sp.x + ep.x)/2, sp.y);
Point c2 = new Point((sp.x + ep.x)/2, ep.y);
path.curveTo(c1.x, c1.y, c2.x, c2.y, ep.x, ep.y);
}
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(new BasicStroke(2));
g2d.translate(40, 130);
g2d.draw(path);
for (int i = 0; i < points.length; ++i) {
g2d.setColor(Color.GRAY);
g2d.fillOval(points[i].x-4, points[i].y-4, 8, 8);
g2d.setColor(Color.BLACK);
g2d.drawOval(points[i].x-4, points[i].y-4, 8, 8);
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Smooth Curve");
frame.setContentPane(new DrawSmoothCurve());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(420, 280);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}