Java Graphics2D 绘图到 BufferedImage

Question

我正忙于摆弄 Java 的 Graphics2D 和绘图，虽然它可以工作，但我不确定如何从这个图形创建一个 BufferedImage，我似乎需要这样做才能将它保存在某个地方。

我有一些非常基本的东西，因为我试图了解它是如何工作的

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);

   }

}

这没问题，除了我得到一个空白 png 作为我的 output.png 并且我不知道为什么虽然我相当确定我的代码是非常错误的

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

您正在用从image.createGraphics() 获得的对象覆盖Graphics2D 对象，该对象在您刚刚创建时是空白的。

将draw 方法简化为：

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，在你实际的Image 的Graphics2D 上执行绘画：

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);
    }


}