java - 为什么BufferedImage没有按照paintComponent方法中绘制的矩形进行切割(其高度计算错误)？

Question

我编写了一个能够让用户剪切图像的应用程序。目前，下面的代码将图像剪切到绘制的矩形上方一点点(其目的是显示用户实际上想要用哪个坐标来剪切图像。)

public class ScreenCaptureRectangle extends JFrame implements MouseListener, MouseMotionListener {

int drag_status = 0, c1, c2, c3, c4;

public void cut() {
    ImagePanel im = new ImagePanel(PicChanges.getNewImage());
    JScrollPane scrollPane = new JScrollPane(im);
    add(scrollPane);
    setSize(500, 400);
    setVisible(true);
    im.addMouseListener(this);
    im.addMouseMotionListener(this);
}

public void draggedScreen() throws Exception {
    int w = c1 - c3;
    int h = c2 - c4;
    w = w * -1;
    h = h * -1;
    Robot robot = new Robot();
    BufferedImage img = robot.createScreenCapture(new Rectangle(c1, c2, w, h));
    File save_path = new File("screen1.jpg");
    ImageIO.write(img, "JPG", save_path);
    System.out.println("Cropped image saved successfully.");
}

@Override
public void mouseClicked(MouseEvent arg0) {
}

@Override
public void mouseEntered(MouseEvent arg0) {
}

@Override
public void mouseExited(MouseEvent arg0) {
}

@Override
public void mousePressed(MouseEvent arg0) {
    repaint();
    c1 = arg0.getX();
    c2 = arg0.getY();
}

@Override
public void mouseReleased(MouseEvent arg0) {
    repaint();
    if (drag_status == 1) {
        c3 = arg0.getX();
        c4 = arg0.getY();
        try {
            repaint();
            draggedScreen();
        } catch (Exception e) {
            e.printStackTrace();
        }
    } else {
        System.out.println("Issue is under construction");
    }
}

@Override
public void mouseDragged(MouseEvent arg0) {
    repaint();
    drag_status = 1;
    c3 = arg0.getX();
    c4 = arg0.getY();
}

@Override
public void mouseMoved(MouseEvent arg0) {
}

public void paint(Graphics g) {
    super.paint(g);
    int w = c1 - c3;
    int h = c2 - c4;
    w = w * -1;
    h = h * -1;
    if (w < 0)
        w = w * -1;
    g.setColor(Color.RED);
    g.drawRect(c1, c2, w, h);
}

public class ImagePanel extends JPanel {

private BufferedImage imageToCut;


public ImagePanel(BufferedImage img) {
    this.imageToCut = img;
    Dimension size = new Dimension(imageToCut.getWidth(null), imageToCut.getHeight(null));
    setPreferredSize(size);
    setMaximumSize(size);
    setMinimumSize(size);
    setSize(size);
}

@Override
protected void paintComponent(Graphics g) {
    g.drawImage(imageToCut, 0, 0, null);
}
}

目前，当用户像这样裁剪图像时:

他明白了:

我的目标是获得以下结果:

我使用鼠标监听器来获取绘制的矩形的坐标，然后使用这些坐标剪切图像。现在图像被切割成不正确的高度(正如我所见)。如果有人能告诉我代码中可能有什么问题，我将不胜感激？谢谢!

Answer 1

感谢我收到的建议，现在用户单击“剪切”按钮后，我不再打开单独的框架来剪切照片，而是将 MouseListener 添加到 JFrame 中，这更加方便和用户友好。根据 MouseListener 的坐标，照片被正确剪切:

public class ImageScreenShot extends JFrame implements MouseListener, MouseMotionListener {

int drag_status = 0, c1, c2, c3, c4;

public int getC1() {
    return c1;
}

public int getC2() {
    return c2;
}

public int getC3() {
    return c3;
}

public int getC4() {
    return c4;
}

public void cut() {
    GraphicalUserInterface.getFrame().addMouseMotionListener(this);
    GraphicalUserInterface.getFrame().addMouseListener(this);
}

public void draggedScreen() throws Exception {
    int w = c1 - c3;
    int h = c2 - c4;
    w = w * -1;
    h = h * -1;
    Robot robot = new Robot();
    BufferedImage img = robot.createScreenCapture(new Rectangle(c1, c2, w, h));
    File save_path = new File("screen1.jpg");
    ImageIO.write(img, "JPG", save_path);
    GraphicalUserInterface.getLabelIcon().setIcon(new ImageIcon(new ImageIcon(img).getImage().getScaledInstance(img.getWidth(), img.getHeight(), Image.SCALE_SMOOTH)));
    JOptionPane.showConfirmDialog(null, "Would you like to save your cropped Pic?");
    if (JOptionPane.YES_OPTION == 0) {
    /**Need to implement some code*/
    } else {
    /**Need to implement some code*/

    }
    System.out.println("Cropped image saved successfully.");
}

@Override
public void mouseClicked(MouseEvent arg0) {
}

@Override
public void mouseEntered(MouseEvent arg0) {
}

@Override
public void mouseExited(MouseEvent arg0) {
}

@Override
public void mousePressed(MouseEvent arg0) {
    c1 = arg0.getXOnScreen();
    c2 = arg0.getYOnScreen();
}

@Override
public void mouseReleased(MouseEvent arg0) {
    if (drag_status == 1) {
        c3 = arg0.getXOnScreen();
        c4 = arg0.getYOnScreen();
        try {
            draggedScreen();
        } catch (Exception e) {
            e.printStackTrace();
        }
    } else {
        System.out.println("Issue is under construction");
    }
}

@Override
public void mouseDragged(MouseEvent arg0) {
    drag_status = 1;
    c3 = arg0.getXOnScreen();
    c4 = arg0.getYOnScreen();
}

@Override
public void mouseMoved(MouseEvent arg0) {
}