Java錯誤？爲什麼要繪製矩形而不是橢圓？

Question

下面的代碼繪製了矩形和2個橢圓。

雖然應該吸取3個橢圓。

我的操作系統是Windows 7的教授64位

我的Java是1.6 x86的也是1.7 x64的測試。

爲什麼？

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

我複製/粘貼您的代碼，並提請2個橢圓你寫的，我做出的唯一改變是您的MigLayout通過null更換，設置用手框架和麪板尺寸和刪除frame.pack()調用：

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重現問題（JA版本「1.8.0-ea」）而不是OpenJDK。正如在另一個答案中指出的那樣，鑽石形狀具有菱形形狀，比例因子是造型變形的根本原因，但不知道這應該是合適的行爲，因此，這些JRE中必定存在一個缺陷。 下面的測試程序工作正常，兩個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中複製上的Java 7，Windows 7中，取出佈局管理器。

我的感覺是，這是由於小浮點值的高標度和不準確性的組合，減少了生成點的數量。

如果您替換的值在0.0363和0.0362之間，則渲染API會中斷。它不再生成一個弧，而是一個正方形。

解決方法是停止將龐大的縮放比例與小尺寸的對象組合在一起。縮小並增大尺寸。