Dan*_*nov 2 java swing bufferedimage image
我一直在尝试制作一个简单的程序,它有一个像工具一样的画笔,打开时它创建了一个JFrame,在其中我放置了一个Canvas,用户可以在其中绘制.现在,我正在尝试使用在退出时调用的saveCanvas方法来保存绘图,但无论我做什么,我都会得到一个黑色图像.这是我的代码:
public class Test{
JFrame f;
Canvas c;
int x=-1, y=-1;
public Test() {
f = new JFrame();
f.setSize(1200, 800);
c = new Canvas(){
@Override
public void paint(Graphics g){
super.paint(g);
}
};
f.add(c);
c.addMouseMotionListener(new MouseMotionListener(){
@Override
public void mouseMoved(MouseEvent e) {
// empty
}
@Override
public void mouseDragged(MouseEvent e){
if(x==-1){
x = e.getX();
y = e.getY();
}
c.getGraphics().fillOval(x, y, 5, 5);
x = e.getX();
y = e.getY();
}
});
f.addWindowListener(new WindowAdapter(){
@Override
public void windowClosing(WindowEvent evt) {
onExit();
}
public void onExit()
{
saveCanvas(c);
System.exit(0);
}
});
f.setVisible(true);
}
public static void main(String[] args) {
Test paintBrush = new Test();
}
public static void saveCanvas(Canvas canvas){
BufferedImage image=new BufferedImage(canvas.getWidth(), canvas.getHeight(),BufferedImage.TYPE_INT_ARGB);
Graphics2D g2=(Graphics2D)image.getGraphics();
boolean x = false;
while(!x){
x = g2.drawImage(image, 0, 0, null);
}
try
{
ImageIO.write(image, "png", new File("C:\\test\\canvas.png"));
}
catch (Exception e) {
}
}
}
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关于可能导致这种情况的任何想法?
这是错的:
Graphics2D g2=(Graphics2D)image.getGraphics();
boolean x = false;
while(!x){
x = g2.drawImage(image, 0, 0, null);
}
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你拿走了Graphics
,image
然后你就image
可以了Graphics
.所以基本上,你正在image
自我绘制.
你想要的可能更像是这样的:
Graphics2D g2=(Graphics2D)image.getGraphics();
canvas.print(g2);
...
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现在,请考虑以下说明:
Canvas
(AWT),而是使用JPanel
(和覆盖paintComponent
)或JLabel
用BufferedImage
(借鉴Graphics
的BufferedImage
,并呼吁repaint()
对JLabel
)(摇摆)getGraphics
在任何组件上使用,请使用方法中Graphics
提供的paintComponent
我正在谈论的小演示示例:
import java.awt.Desktop;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
public class Test {
JFrame f;
JLabel c;
BufferedImage image;
int x = -1, y = -1;
public Test() {
f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
image = new BufferedImage(1200, 800, BufferedImage.TYPE_INT_ARGB);
c = new JLabel(new ImageIcon(image));
f.add(c);
c.addMouseMotionListener(new MouseMotionListener() {
@Override
public void mouseMoved(MouseEvent e) {
// empty
}
@Override
public void mouseDragged(MouseEvent e) {
if (x == -1) {
x = e.getX();
y = e.getY();
}
image.getGraphics().fillOval(x, y, 5, 5);
c.repaint();
x = e.getX();
y = e.getY();
}
});
f.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent evt) {
onExit();
}
public void onExit() {
try {
File output = new File("C:\\test\\canvas.png");
if (!output.getParentFile().exists()) {
output.getParentFile().mkdirs();
}
ImageIO.write(image, "png", output);
Desktop.getDesktop().open(output);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
Test paintBrush = new Test();
}
});
}
}
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