高级绘制特性：抗锯齿和双缓存

现在的绘制系统越来越成型，上几节中，我们会发现我们的圆形非常的不平滑，这一节我们来实现如何抗锯齿。

实现效果如下

通过在边缘的位置渲染使用不同深度的颜色或者利用透明度这样的概念来实现抗锯齿。使得边缘的颜色存在灰度。人眼在效果上看上去就相对平滑很多。Anti-Aliased

使用框架提供的方式。完整方案请查看Java官方文档

双缓存：主要应用于动画上，解决闪烁问题。

完整代码

import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.Dimension;
import java.awt.Color;
import java.awt.geom.Ellipse2D;
import java.awt.RenderingHints;
import java.awt.BasicStroke;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class AlgoFrame extends JFrame{

    private int canvasWidth;
    private int canvasHeight;

    public AlgoFrame(String title, int canvasWidth, int canvasHeight){

        super(title);

        this.canvasWidth = canvasWidth;
        this.canvasHeight = canvasHeight;

        AlgoCanvas canvas = new AlgoCanvas();
        setContentPane(canvas);
        pack();

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        setVisible(true);
    }

    public AlgoFrame(String title){

        this(title, 1024, 768);
    }

    public int getCanvasWidth(){return canvasWidth;}
    public int getCanvasHeight(){return canvasHeight;}

    private class AlgoCanvas extends JPanel{

        public AlgoCanvas(){
            // 双缓存
            super(true);
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2d = (Graphics2D)g;

            // 抗锯齿
            RenderingHints hints = new RenderingHints(
                                            RenderingHints.KEY_ANTIALIASING,
                                            RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.addRenderingHints(hints);

            // 具体绘制
            AlgoVisHelper.setColor(g2d, Color.BLUE);
            AlgoVisHelper.fillCircle(g2d, canvasWidth/2,canvasHeight/2,200);

            AlgoVisHelper.setStrokeWidth(g2d,5);
            AlgoVisHelper.setColor(g2d, Color.RED);
            AlgoVisHelper.strokeCircle(g2d, canvasWidth/2,canvasHeight/2,200);
        }

        @Override
        public Dimension getPreferredSize(){
            return new Dimension(canvasWidth, canvasHeight);
        }

    }
}