java - 如何使用 ImageIO 保存通过 Graphics 创建的 Java 图像

Question

我正在使用图形库创建图像，并尝试使用 BufferedImage 和 ImageIO 保存创建的图像。运行后，我的图像弹出，但保存的图像只是黑色。

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;

public class drawing extends Canvas {

    public static void main(String[] args) {
        JFrame frame = new JFrame("My Drawing");
        Canvas canvas = new drawing();
        canvas.setSize(400, 400);
        canvas.setBackground(Color.CYAN);
        frame.add(canvas);
        frame.pack();
        frame.setVisible(true);
    }
    public void paint(Graphics g) {
        Rectangle bb = new Rectangle(100, 100, 200, 200);
        g.setColor(Color.yellow);
        try {
            mickey(g, bb);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void boxOval(Graphics g, Rectangle bb) {
        g.fillOval(bb.x, bb.y, bb.width, bb.height);
        g.setColor(Color.blue);
    }
    public void mickey(Graphics g, Rectangle bb) throws IOException {
        boxOval(g, bb);
        int dx = bb.width / 2;
        int dy = bb.height / 2;
        g.setColor(Color.RED);
        Rectangle half = new Rectangle(bb.x, bb.y, dx, dy);
        half.translate(-dx / 2, -dy / 2);
        boxOval(g, half);
        half.translate(dx * 2, 0);
        boxOval(g, half);
        half.translate(dx / 10, 50);
        boxOval(g, half);

        BufferedImage buff = new BufferedImage(dx, dy, BufferedImage.TYPE_INT_RGB);
        File file = new File("mickey.png");
        System.out.println("saving....");
        ImageIO.write(buff, "png", file);
        System.out.println("saved!");
    }

}

我希望保存到 mickey.png 的图像与我之前在 mickey 方法中绘制的图像相同。

Answer 1

你需要这样做:

    BufferedImage buff = new BufferedImage(dx, dy, BufferedImage.TYPE_INT_RGB);
    this.paint(buff.getGraphics()); // call paint to draw on the image
    File file = new File("mickey.png");
    System.out.println("saving....");
    ImageIO.write(buff, "png", file);
    System.out.println("saved!");

重新安排代码以在 mickey() 和 Paint() 外部进行保存。