Java Graphics2D绘制到BufferedImage中

Question

我忙于摆弄Java的Graphics2D和绘图，尽管它工作正常，但我不确定如何从该图形创建一个BufferedImage，看起来我需要这样做才能将它保存到某个位置。

我有一些非常基本的，因为我想知道这是如何工作

import javax.swing.*; 
import javax.imageio.*; 
import java.awt.*; 
import java.awt.image.*; 
import java.io.*; 

public class myFrame { 

    public static void main(String[] args) { 

     JFrame lv_frame = new JFrame(); 
     lv_frame.setTitle("Drawing"); 
     lv_frame.setSize(300, 300); 
     lv_frame.setDefaultCloseOperation(JInternalFrame.DISPOSE_ON_CLOSE); 

     lv_frame.add(new drawingPanel(5, 5)); 

     lv_frame.setVisible(true); 

    } 

} 

class drawingPanel extends JPanel { 

    public drawingPanel(int x, int y) { 
    } 

    public void draw(Graphics graphic) { 

     Graphics2D graphic2D = (Graphics2D) graphic; 
     graphic2D.fillArc(0, 0, 50, 50, 0, 45); 
     graphic2D.fillArc(0, 0, 50, 50, 135, 45); 

     BufferedImage image = new BufferedImage(100, 100, BufferedImage.TYPE_INT_BGR); 

     try { 
     graphic2D = image.createGraphics(); 
     File output = new File("output.png"); 
     ImageIO.write(image, "png", output); 
     } catch(IOException log) { 
     System.out.println(log); 
     } 

    } 

    public void paintComponent(Graphics graphic) { 

     super.paintComponent(graphic); 
     draw(graphic); 

    } 

} 

该工程确定，除了我得到一个空白PNG作为我output.png，我不知道为什么，虽然我“M相当肯定我的代码是可怕的错误

工作版本

import javax.swing.*; 
import javax.imageio.*; 
import java.awt.*; 
import java.awt.image.*; 
import java.io.*; 

public class myFrame { 

    public static void main(String[] args) { 

     JFrame lv_frame = new JFrame(); 
     lv_frame.setTitle("Drawing"); 
     lv_frame.setSize(300, 300); 
     lv_frame.setDefaultCloseOperation(JInternalFrame.DISPOSE_ON_CLOSE); 

     lv_frame.add(new drawingPanel()); 

     lv_frame.setVisible(true); 

    } 

} 

class drawingPanel extends JPanel { 

    public void paintComponent(Graphics graphic) { 

     super.paintComponent(graphic); 
     draw(graphic); 
     saveImage(); 

    } 

    public void draw(Graphics graphic) { 

     Graphics2D graphic2D = (Graphics2D) graphic; 

     Color color = Color.decode("#DDDDDD"); 
     graphic2D.setPaint(color); 

     graphic2D.fillArc(0, 0, 50, 50, 0, 45); 
     graphic2D.fillArc(0, 0, 50, 50, 135, 45); 

    } 

    public void saveImage() { 

     BufferedImage image = new BufferedImage(100, 100, BufferedImage.TYPE_INT_BGR); 
     Graphics2D graphic2D = image.createGraphics(); 

     try { 
     File output = new File("output.png"); 
     draw(graphic2D); 
     ImageIO.write(image, "png", output); 
     } catch(IOException log) { 
     System.out.println(log); 
     } 

    } 

} 

Answer 1

要覆盖Graphics2D与您从image.createGraphics()获得的对象相对应，它在您刚创建时为空。

简化draw方法：

public void draw(Graphics graphic) { 

     Graphics2D graphic2D = (Graphics2D) graphic; 
     graphic2D.fillArc(0, 0, 50, 50, 0, 45); 
     graphic2D.fillArc(0, 0, 50, 50, 135, 45); 

} 

然后从另一个方法调用它，对进行绘画的实际Image的Graphics2D：

public void saveAsImage(){ 

BufferedImage image = new BufferedImage(100, 100, BufferedImage.TYPE_INT_BGR); 

try { 
     Graphics2D graphic = image.createGraphics(); 
     File output = new File("output.png"); 
     draw(graphic); // actual drawing on your image 
     ImageIO.write(image, "png", output); 
    } catch(IOException log) { 
     System.out.println(log); 
    } 


}