BufferedImage 中的图像捕获

Question

我是新来的，对 Java 也很陌生。 我正在制作一个可以选择图像区域的应用程序，它只是返回选定的坐标。问题是，它不是显示图像，而是显示黑色区域而不是图像。 还尝试了 BufferedImage.TYPE_INT_ARGB，现在它显示了一个空白区域。

这里是代码。请帮忙。

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


public class ScreenCaptureRectangle {

Rectangle captureRect;

ScreenCaptureRectangle(final Image im) {
    final BufferedImage screenCopy = new BufferedImage(
            im.getWidth(null),
            im.getHeight(null),
            BufferedImage.TYPE_INT_ARGB);
    final BufferedImage screenCopy1 = new BufferedImage(
            im.getWidth(null),
            im.getHeight(null),
            BufferedImage.TYPE_INT_ARGB);

    final JLabel screenLabel = new JLabel(new ImageIcon(screenCopy));
    JScrollPane screenScroll = new JScrollPane(screenLabel);

    screenScroll.setPreferredSize(new Dimension(
            (int)(im.getWidth(null)),
            (int)(im.getHeight(null))));

    JPanel panel = new JPanel(new BorderLayout());
    panel.add(screenScroll, BorderLayout.CENTER);

    final JLabel selectionLabel = new JLabel(
            "Drag a rectangle in the screen shot!");
    panel.add(selectionLabel, BorderLayout.SOUTH);

    repaint(screenCopy1, screenCopy);
    screenLabel.repaint();

    screenLabel.addMouseMotionListener(new MouseMotionAdapter() {

        Point start = new Point();

        @Override
        public void mouseMoved(MouseEvent me) {
            start = me.getPoint();
            repaint(screenCopy1, screenCopy);
            selectionLabel.setText("Start Point: " + start);
            screenLabel.repaint();
        }

        @Override
        public void mouseDragged(MouseEvent me) {
            Point end = me.getPoint();
            captureRect = new Rectangle(start,
                    new Dimension(end.x-start.x, end.y-start.y));
            repaint(screenCopy1, screenCopy);
            screenLabel.repaint();
            selectionLabel.setText("Rectangle: " + captureRect);
        }
    });

    JOptionPane.showMessageDialog(null, panel);

    System.out.println("Rectangle of interest: " + captureRect);
}  


public void repaint(BufferedImage orig, BufferedImage copy) {
    Graphics2D g = copy.createGraphics();
    g.drawImage(orig,0,0, null);
    if (captureRect!=null) {
        g.setColor(Color.RED);
        g.draw(captureRect);
        g.setColor(new Color(255,255,255,150));
        g.fill(captureRect);
    }
    g.dispose();
}

public static void main(String[] args) throws Exception {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            try {
                new ScreenCaptureRectangle(ImageIO.read(new File("Desert.jpg")));
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    });
}
}

Answer 1

您的问题是您永远不会将原始图像（im，从"Desert.jpg" 读取）绘制到您的任何screenCopy 或screenCopy1 图像中，您只会创建相同大小的空BufferedImages。这些“副本”将始终保持空白。