java - PNG 文件另存为全黑图像

Question

所以，我正在尝试做一个绘画程序，我添加了一些功能，但现在我希望能够保存图片。我打开程序，画一幅画，保存它，一切正常!除了图像现在全黑之外。预先感谢您!

(请告诉我是否有不好的代码，因为我仍然是一个学习Java程序员，这对我将来有很大的好处)

类(class):

主类:

import javax.swing.JFrame;



public class Test{
public static void main(String args[]){

    Ploofer ploof = new Ploofer();
    ploof.setSize(1000, 950);
    PumpkinPie f = new PumpkinPie(ploof);

    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setSize(1000,1000);
    f.setResizable(false);
    f.setVisible(true);
    f.setLayout(null);
    f.add(ploof);
}
}

“Ploofer”类:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;

import javax.swing.JPanel;


public class Ploofer extends JPanel{

private static boolean calledOnce = false;
private BufferedImage img = new BufferedImage(1000, 950,       BufferedImage.TYPE_INT_RGB);
static private Color backgroundColor = null;
private PumpkinPie pObj;

@Override
public void paintComponent(Graphics g){

    if(calledOnce == false){
        pObj = new PumpkinPie(this);
        calledOnce = true;
    }

    super.paintComponent(g);
    private Graphics2D g2d = img.createGraphics();

    if(pObj.colour != null){
            g2d.setColor(pObj.colour);
    }

    else{
            g2d.setColor(Color.BLACK);
    }

    if(pObj.setToBackgroundColor == true){
        pObj.colour = backgroundColor;
        pObj.setToBackgroundColor = false;
    }

    if(pObj.changeBackgroundColor == true){
        backgroundColor = pObj.colour;
        this.setBackground(backgroundColor);
        g2d.setBackground(backgroundColor);
        pObj.changeBackgroundColor = false;
        update(g2d);
        update(g);
    }

    if(pObj.wipe == true){
        g2d.clearRect(0, 0, img.getWidth(), img.getHeight());
        g.dispose();
        g2d.setBackground(Color.WHITE);
        g.drawImage(img, 0, 0, null);
        pObj.wipe = false;
        repaint();
    }

    if(pObj.draw == true){
        g2d.fillRect(pObj.x, pObj.y, 8, 8);
        pObj.draw = false;
    }



    if(img != null){
        g.drawImage(img, 0, 0, null);
    }
}

public BufferedImage getImage(){
    return img;
}

}

“南瓜派”类:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.border.Border;

public class PumpkinPie extends JFrame{

public int x;
public int y;
static public boolean draw = false;
static public boolean changeBackgroundColor = false;
static public boolean setToBackgroundColor = false;
static public boolean wipe = false;
static public Color colour = Color.WHITE;
Box box;

private JMenuBar menuBar;
private JMenu file, edit;
private JMenuItem save, saveas, exit, open, clear, changeBackground;
private JPanel colourButton;
private JButton saveButton;
private Icon eraser;
private JLabel eraserLabel;
private JFileChooser fc;

Ploofer ploof = new Ploofer();

public PumpkinPie(JPanel panel){
    super("SPLAT! SPLAT!");

    file = new JMenu("File");
    edit = new JMenu("Edit");
    box = Box.createHorizontalBox();

    menuBar = new JMenuBar();

    open = new JMenuItem("Open file");      
    save = new JMenuItem("Save");
    saveas = new JMenuItem("Save as...");
    exit = new JMenuItem("Exit");
    clear = new JMenuItem("Clear");
    changeBackground = new JMenuItem("Change background color");
    colourButton = new JPanel();
    eraserLabel = new JLabel();
    eraser = new ImageIcon(getClass().getResource("/Resources/Eraser.png"));
    fc = new JFileChooser();
    fc.setCurrentDirectory(new File("C:\\Users\\" + System.getProperty("user.name") + "\\Pictures"));
    fc.setDialogTitle("Choose a location...");
    saveButton = new JButton("Save");

    panel.setSize(1000, 950);
    panel.setLocation(0, 50);
    colourButton.setSize(50, 50);
    colourButton.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    eraserLabel.setIcon(eraser);
    eraserLabel.setSize(50, 50);
    eraserLabel.setLocation(50, 0);

    this.setJMenuBar(menuBar);
    setLayout(new BorderLayout());

    menuBar.add(file);
    menuBar.add(edit);
    file.add(open);
    file.add(save);
    file.add(saveas);
    file.add(exit);
    edit.add(clear);
    edit.add(changeBackground);
    setLayout(null);
    add(colourButton);
    add(eraserLabel);

    MouseMoveHandlerer mouseMoveHandler = new MouseMoveHandlerer();
    MouseHandlerer mouseHandler = new MouseHandlerer();
    ButtonHandlerer buttonHandler = new ButtonHandlerer();

    panel.addMouseMotionListener(mouseMoveHandler);
    eraserLabel.addMouseListener(mouseHandler);
    clear.addActionListener(buttonHandler);
    colourButton.addMouseListener(mouseHandler);
    changeBackground.addActionListener(buttonHandler);
    save.addActionListener(buttonHandler);
    saveas.addActionListener(buttonHandler);
}

private class MouseMoveHandlerer extends MouseMotionAdapter{        
    public void mouseDragged(MouseEvent event){
        x = event.getX();
        y = event.getY();
        draw = true;
        repaint();
    }

}

private class MouseHandlerer extends MouseAdapter{
    public void mouseClicked(MouseEvent event){
        if(event.getSource() == colourButton){
            colour = JColorChooser.showDialog(null, "Choose a colour", colour);
            colourButton.setBackground(colour);
        }
        else if(event.getSource() == eraserLabel){
            setToBackgroundColor = true;
            repaint();
            colourButton.setBackground(colour);
        }
    }
}

private class ButtonHandlerer implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent event) {
        if(event.getSource() == save){
        }
        else if(event.getSource() == saveas){
            if(fc.showSaveDialog(saveButton) == JFileChooser.APPROVE_OPTION){
                try{
                    ImageIO.write(ploof.getImage(), "PNG", new      File(fc.getSelectedFile().getPath() + ".png"));
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        }
        else if (event.getSource() == clear){
            wipe = true;
            repaint();
        }
        else{
            changeBackgroundColor = true;
            repaint();
        }
    }

}

}

Answer 1

无法真正遵循您的绘画逻辑，但有一些评论:

1. 不要直接调用 update(...)。 Swing 将在适当的时候调用该方法。绘画方法应该只关心绘画逻辑。

2. 不要使用paintComponent()方法创建BufferedImage。使用 BufferedImage 的要点是将图像绘制到 BufferedImage 上一次，然后在 PaintComponent() 方法中绘制 BufferedImage。

如果您每次都要重新创建 BufferedImage，那么您不妨直接在面板的 Graphics 上绘制。由于您似乎有一堆可以更改的变量，我猜您应该直接在面板上进行绘画，而不必担心 BufferedImage。

Except for the fact that the image is now completely black

您可以根据需要创建 BufferedImage，而不是尝试在 PaintCompnent() 方法中创建图像。查看ScreenImage类(class)。它将允许您创建任何 Swing 组件的图像。

使用此类来创建/保存图像的代码将类似于；

BufferedImage bi = ScreenImage.createImage(yourPanel);
ScreenImage.writeImage(bi, "panel-image.png");

您可能还想查看Custom Painting Approaches了解在 BufferedImage 上绘画和在 PaintComponent() 方法中绘画之间的差异。