如何禁用java.awt.Graphics.fillRect(int x,int y,int width,int height)的效果？

我使用java.awt.Graphics.fillRect(int x,int y,int width,int height)在图像上添加彩色矩形.

Graphics imageGraphics = image.createGraphics();
Color color = new Color(0,0,0,100);
imageGraphics.setColor(color);
imageGraphics.fillRect(0, 0, 800, 600);

所以图像已被反转,看起来像这样：

之后,我想部分清除黑色透明矩形并显示原始图像.
imageGraphics.clearRect(100,100,100,100);
但效果是这样的：

我的要求是：

我想知道为什么它不起作用,有没有其他方法来实现它？

下面的示例创建两个Rectangle,一个是我们要填充的区域,一个是我们要显示的区域,然后从第一个区域中减去第二个(创建窗口),然后将结果绘制在图像顶​​部

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Area;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ShowArea {

    public static void main(String[] args) {
        new ShowArea();
    }

    public ShowArea() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;

        public TestPane() {
            try {
                img = ImageIO.read(new File("sample.png"));
                Rectangle bounds = new Rectangle(0, 0, img.getWidth(), img.getHeight());
                Rectangle clip = new Rectangle(150, 10, 100, 100);

                Area area = new Area(bounds);
                area.subtract(new Area(clip));

                Graphics2D g2d = img.createGraphics();
                g2d.setColor(Color.BLACK);
                g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
                g2d.fill(area);
                g2d.dispose();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return img == null ? new Dimension(200, 200) :  new Dimension(img.getWidth(), img.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int x = (getWidth() - img.getWidth()) / 2;
            int y = (getHeight() - img.getHeight()) / 2;
            g2d.drawImage(img, x, y, this);
            g2d.dispose();
        }

    }

}

如果我正在进行某种绘制程序,我会在paintComponent方法中完成所有操作,或者以某种方式使它不影响原始图像,否则你基本会破坏图像直到你重新加载它

另一种解决方案可能是拍摄您想要保留的原始区域的副本,然后将其重新打印回来,例如……

img = ImageIO.read(new File("sample.png"));
// This is the portion of the image we want to save...
BufferedImage cutout = img.getSubimage(150, 10, 100, 100);
// This is the area we want to paint over...
Rectangle bounds = new Rectangle(0, 0, img.getWidth(), img.getHeight());

Graphics2D g2d = img.createGraphics();
g2d.setColor(Color.BLACK);
// Save the current Composite so we can reset it...
Composite comp = g2d.getComposite();
// Apply the composite and fill the area...
g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
g2d.fill(area);
// Reset the composite 
g2d.setComposite(comp);
// Draw the part of the image we saved previously...
g2d.drawImage(cutout, 150, 10, this);
g2d.dispose();