Java错误？为什么要绘制矩形而不是椭圆？

Question

下面的代码绘制了矩形和2个椭圆。

虽然应该吸取3个椭圆。

我的操作系统是Windows 7的教授64位

我的Java是1.6 x86的也是1.7 x64的测试。

为什么？

package tests; 

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

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

import net.miginfocom.swing.MigLayout; 

public class AntialiacingScaleTester { 

    public static void main(String[] args) { 

     SwingUtilities.invokeLater(new Runnable() { 

      @Override 
      public void run() { 

       JPanel circlePanel = new JPanel() { 
        @Override 
        public void paintComponent(Graphics g) { 

         super.paintComponent(g); 

         Graphics2D g2d = (Graphics2D)g; 
         g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

         g2d.setColor(Color.RED); 
         g2d.setStroke(new BasicStroke(1)); 
         //g2d.drawOval(0, 0, 200, 200); 
         g2d.draw(new Ellipse2D.Double(0, 0, 200, 200)); 

         AffineTransform old = g2d.getTransform(); 

         g2d.setColor(Color.GREEN); 
         g2d.scale(1000, 1000); 
         g2d.setStroke(new BasicStroke(0.001f)); 
         g2d.draw(new Ellipse2D.Double(0, 0, 0.225, 0.225)); 

         g2d.setColor(Color.BLUE); 
         g2d.scale(10, 10); 
         g2d.setStroke(new BasicStroke(0.001f)); 
         g2d.draw(new Ellipse2D.Double(0, 0, 0.025, 0.025)); 

         g2d.setTransform(old); 

        } 
       }; 

       JFrame frame = new JFrame(); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 


       //frame.setLayout(new MigLayout("fill")); 
       //frame.add(circlePanel, "w 300, h 300, grow"); 

       //frame.add(circlePanel); 

       frame.setLayout(null); 
       circlePanel.setBounds(new Rectangle(0, 0, 300, 300)); 
       frame.add(circlePanel); 

       frame.setBounds(0, 0, 350, 300); 

       //frame.pack(); 
       frame.setVisible(true); 

      } 
     }); 

    } 

} 

Answer 1

我复制/粘贴您的代码，并提请2个椭圆你写的，我做出的唯一改变是您的MigLayout通过null更换，设置用手框架和面板尺寸和删除frame.pack()调用：

import java.awt.BasicStroke; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.RenderingHints; 
import java.awt.geom.AffineTransform; 
import java.awt.geom.Ellipse2D; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

public class Test { 
    /** 
    * @param args 
    */ 
    public static void main(String[] args) { 
     JPanel circlePanel = new JPanel() { 
      @Override 
      public void paint(Graphics g) { 

       Graphics2D g2d = (Graphics2D) g; 
       g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

       g2d.setStroke(new BasicStroke(1)); 
       //g2d.drawOval(0, 0, 200, 200); 
       g2d.draw(new Ellipse2D.Double(0, 0, 200, 200)); 

       AffineTransform old = g2d.getTransform(); 

       g2d.scale(10000, 10000); 
       g2d.setStroke(new BasicStroke(0.001f)); 
       g2d.draw(new Ellipse2D.Double(0, 0, 0.025, 0.025)); 

       g2d.setTransform(old); 

      } 
     }; 

     JFrame frame = new JFrame(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     frame.setLayout(null); 
     circlePanel.setBounds(new Rectangle(0, 0, 300, 300)); 
     frame.add(circlePanel); 

     frame.setBounds(0, 0, 350, 300); 

     //frame.pack(); 
     frame.setVisible(true); 
    } 
} 

更新： 能使用Oracle JDK重现问题（JA版本“1.8.0-ea”）而不是OpenJDK。正如在另一个答案中指出的那样，钻石形状具有菱形形状，比例因子是造型变形的根本原因，但不知道这应该是合适的行为，因此，这些JRE中必定存在一个缺陷。 下面的测试程序工作正常，两个JRE的：

import java.awt.BasicStroke; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.RenderingHints; 
import java.awt.geom.AffineTransform; 
import java.awt.geom.Ellipse2D; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

public class Test { 
    /** 
    * @param args 
    */ 
    public static void main(String[] args) { 
     JPanel circlePanel = new JPanel() { 
      @Override 
      public void paint(Graphics g) { 

       Graphics2D g2d = (Graphics2D) g; 
       g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

       g2d.setStroke(new BasicStroke(1)); 
       //g2d.drawOval(0, 0, 200, 200); 
       g2d.draw(new Ellipse2D.Double(0, 0, 200, 200)); 

       AffineTransform old = g2d.getTransform(); 

       g2d.scale(10, 10); 
       g2d.setStroke(new BasicStroke(1.0f)); 
       g2d.draw(new Ellipse2D.Double(0, 0, 25.0, 25.0)); 

       g2d.setTransform(old); 

      } 
     }; 

     JFrame frame = new JFrame(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     frame.setLayout(null); 
     circlePanel.setBounds(new Rectangle(0, 0, 300, 300)); 
     frame.add(circlePanel); 

     frame.setBounds(0, 0, 350, 300); 

     //frame.pack(); 
     frame.setVisible(true); 
    } 
} 

Answer 2

在Eclipse中复制上的Java 7，Windows 7中，取出布局管理器。

我的感觉是，这是由于小浮点值的高标度和不准确性的组合，减少了生成点的数量。

如果您替换的值在0.0363和0.0362之间，则渲染API会中断。它不再生成一个弧，而是一个正方形。

解决方法是停止将庞大的缩放比例与小尺寸的对象组合在一起。缩小并增大尺寸。