Develop Reference

Display moving image in Java Swing

I'm trying to display a high-width image in Java Swing (say 2000x100, like a heart rate strip). I need to show only a window of 500 width while it is slightly moving towards left. My current code (a bit complicated, it also has unnecessary animations) does it, but the feature I need to add is: The end of image should be concatenated with the beginning of the image. So it always repeats showing over and over.
In short, I need to join the two ends of image! How can I do that?
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.LinearGradientPaint;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Point2D;
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.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class SlidingAnimation {
public static void main(String[] args) {
new SlidingAnimation();
}
public SlidingAnimation() {
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);
JPanel j = new JPanel();
j.add(new AnimatedBar(true));
frame.add(j);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}
class AnimatedBar extends JPanel {
private BufferedImage img;
private Timer timer;
private long startTime = -1;
private int playTime = 4000;
private int window = 500;
private int moveX=0;
public static boolean keepRunning=true;
private float progress;
public AnimatedBar(boolean x) {
try {
if(x)
img = ImageIO.read(new File("strip2.jpg"));
else
img=null;
} catch (IOException ex) {
ex.printStackTrace();
}
if(x){
timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (startTime == -1) {
startTime = System.currentTimeMillis();
} else {
long currentTime = System.currentTimeMillis();
long diff = currentTime - startTime;
if (diff >= playTime) {
diff = 0;
startTime = -1;
}
progress = diff / (float) playTime;
}
repaint();
}
});
timer.start();
}
}
#Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(50, 50) : new Dimension(img.getWidth()/3, img.getHeight());
}
protected BufferedImage generateImage() {
BufferedImage buffer = new BufferedImage(img.getWidth(), img.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = buffer.createGraphics();
g2d.setBackground(new Color(0, 0, 0, 0));
g2d.clearRect(0, 0, buffer.getWidth(), buffer.getHeight());
// g2d.drawImage(img, 500, 0, this);
g2d.drawImage(img,0,0,500,100,(moveX++),0,window+moveX,100,this);
float startAt = progress- 0.05f;
float endAt = progress + 0.05f;
if (endAt <= 0.1f) {
startAt = 0;
endAt = Math.max(0.1f, progress);
} else if (endAt >= 1f) {
endAt = 1f;
startAt = progress;
}
LinearGradientPaint lgp = new LinearGradientPaint(
new Point2D.Float(0, 0),
new Point2D.Float(img.getWidth(), 0),
new float[]{startAt, endAt},
new Color[]{new Color(0, 0, 0, 0), Color.RED});
g2d.setPaint(lgp);
g2d.setComposite(AlphaComposite.DstOut.derive(1f));
g2d.fill(new Rectangle(0, 0, img.getWidth(), img.getHeight()));
g2d.dispose();
return buffer;
}
public void setImg(BufferedImage img) {
this.img = img;
}
#Override
protected void paintComponent(Graphics g) {
if(keepRunning==false){
img=null;
}
else{
try {
img = ImageIO.read(new File("strip2.jpg"));
} catch (IOException e) {
}
}
super.paintComponent(g);
if (img != null) {
Graphics2D g2d = (Graphics2D) g.create();
int y = (getHeight() - img.getHeight()) / 2;
int x = (getWidth() - img.getWidth()/3) / 2;
g2d.drawImage(generateImage(), x, y, this);
g2d.dispose();
}
}
}

To join the ends, paint the image twice as seen in this answer. The first paint would be the end of the image. The second paint would be the start of the image, offset by the width the end goes to.
E.G.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import java.net.URL;
import javax.imageio.ImageIO;
public class HeartBeat {
public static void main(String[] args) throws Exception {
URL url = new URL("http://i.stack.imgur.com/i8UJD.jpg");
final BufferedImage bi = ImageIO.read(url);
Runnable r = new Runnable() {
#Override
public void run() {
final BufferedImage canvas = new BufferedImage(
bi.getWidth(), bi.getHeight(),
BufferedImage.TYPE_INT_RGB);
final JLabel animationLabel = new JLabel(new ImageIcon(canvas));
ActionListener animator = new ActionListener() {
int x = 0;
#Override
public void actionPerformed(ActionEvent e) {
Graphics2D g = canvas.createGraphics();
// paint last part of image in left of canvas
g.drawImage(bi, x, 0, null);
// paint first part of image immediately to the right
g.drawImage(bi, x + bi.getWidth(), 0, null);
// reset x to prevent hitting integer overflow
if (x%bi.getWidth()==0) x = 0;
g.dispose();
animationLabel.repaint();
x--;
}
};
Timer timer = new Timer(40, animator);
timer.start();
JOptionPane.showMessageDialog(null, animationLabel);
timer.stop();
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency
SwingUtilities.invokeLater(r);
}
}

The end of image should be concatenated with the beginning of the image. So it always repeats showing
Check out the Marquee Panel. You can add a JLabel with an ImageIcon to the MarqueePanel.
The MarqueePanel provides various method to customize the scrolling.
Edit:
The basic code would be:
MarqueePanel panel = new MarqueePanel();
panel.setWrap(true);
panel.setWrapAmount(0);
panel.setPreferredWidth(250);
JLabel label = new JLabel( new ImageIcon( "heartbeat.jpg" ) );
panel.add( label );
frame.add( panel );
If you want the image to fully appear at the left when it is displayed you can change the startScrolling() method and use scrollOffset = 0;.

Call JDialog from JDialog

I'm trying to build an application, in which allows calling JDialog from JDialog. I've tried it, but at the time of the call dialog B of A, B dialog appears and then immediately disappears. Is there a solution to these problems?
My code :
I have a class A which extends javax.swing.JDialog. Then there is a label that has the action to call dialog from class PadAndZoom as below:
private void lblSuratRekomendasiMouseClicked(java.awt.event.MouseEvent evt) {
try {
PadAndZoom app = new PadAndZoom();
BufferedImage img = ImageIO.read(PadAndZoom.class.getResource("/tampilan/background5.jpg"));
app.tes(img);
} catch (IOException ex) {
Logger.getLogger(RincianBukuBesar.class.getName()).log(Level.SEVERE, null, ex);
}
}
then I have one more class to be invoked by the method lblSuratRekomendasiMouseClicked (java.awt.event.MouseEvent evt) of class A
package dispertasih;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;
public class PadAndZoom implements ChangeListener {
BufferedImage image;
PanPanelX label;
public void stateChanged(ChangeEvent e) {
int value = ((JSlider) e.getSource()).getValue();
double scale = value / 200.0;
BufferedImage scaled = getScaledImage(scale);
label.setImage(scaled);
}
public BufferedImage getScaledImage(double scale) {
int w = (int)(scale*image.getWidth());
int h = (int)(scale*image.getHeight());
BufferedImage bi = new BufferedImage(w, h, image.getType());
Graphics2D g2 = bi.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
AffineTransform at = AffineTransform.getScaleInstance(scale, scale);
g2.drawRenderedImage(image, at);
g2.dispose();
return bi;
}
public PanPanelX getContent() {
// createAnImage();
label = new PanPanelX(image);
//label.setHorizontalAlignment(JLabel.CENTER);
return label;
}
public void createAnImage(BufferedImage imgbuf) {
int w = 500;
int h = 500;
int type = BufferedImage.TYPE_INT_RGB; // many options
image = imgbuf;
}
public JSlider getControl() {
JSlider slider = new JSlider(JSlider.HORIZONTAL, 50, 200, 50);
slider.setMajorTickSpacing(50);
slider.setMinorTickSpacing(10);
slider.setPaintTicks(true);
slider.setPaintLabels(true);
slider.addChangeListener(this);
return slider;
}
public void tes(BufferedImage img) {
PadAndZoom app = new PadAndZoom();
JDialog f = new JDialog();
JButton b = new JButton();
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException e) { }
app.createAnImage(img);
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.getContentPane().add(new JScrollPane(app.getContent()));
//f.getContentPane().add(new JButton("tessss"));
f.getContentPane().add(app.getControl(), "Last");
f.setSize(400, 400);
f.setLocation(200,200);
f.setVisible(true);
}
}
class PanPanelX extends JPanel {
public int x, y;
public int width = 800, height = 800;
BufferedImage img;
public final static RenderingHints textRenderHints = new RenderingHints(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
public final static RenderingHints imageRenderHints = new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
public final static RenderingHints renderHints = new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
static int startX, startY;
public void setImage(BufferedImage img) {
this.img = img;
revalidate();
repaint();
}
public PanPanelX(BufferedImage img) {
x = 20;
y = 20;
this.img = img;
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent me) {
super.mousePressed(me);
startX = me.getX();
startY = me.getY();
}
});
addMouseMotionListener(new MouseMotionAdapter() {
#Override
public void mouseDragged(MouseEvent me) {
super.mouseDragged(me);
if (me.getX() < startX) {//moving image to right
x -= 2;
} else if (me.getX() > startX) {//moving image to left
x += 2;
}
if (me.getY() < startY) {//moving image up
y -= 2;
} else if (me.getY() > startY) {//moving image to down
y += 2;
}
repaint();
}
});
}
#Override
protected void paintComponent(Graphics grphcs) {
super.paintComponent(grphcs);
Graphics2D g2d = (Graphics2D) grphcs;
//turn on some nice effects
applyRenderHints(g2d);
g2d.drawImage(img, x, y, null);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(width, height);
}
public static void applyRenderHints(Graphics2D g2d) {
g2d.setRenderingHints(textRenderHints);
g2d.setRenderingHints(imageRenderHints);
g2d.setRenderingHints(renderHints);
}
}
thanks u ..

Trying to paint image to JFrame with Java BufferedImage, Graphics

I'm trying to capture the screen and then paint the image to a JFrame recursively while scaling the image (to create that effect you get when you look at a mirror in a mirror).
I'm having trouble with my code - it doesn't paint any graphics. What am I doing wrong?
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
public class ScreenCapture extends JFrame {
BufferedImage screenCapture;
Graphics screenCaptureGraphics;
private static int recurseCount = 0;
private static float $scale = 0.9f;
private static float scale = 1.0f;
private static int height;
private static int width;
ScreenCapture() {
try {
screenCapture = new Robot().createScreenCapture(
new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()) );
height = screenCapture.getHeight();
width = screenCapture.getWidth();
setSize(new Dimension(width, height));
addWindowListener(new LocalWindowListener());
Graphics g = recursiveDraw(screenCapture, getGraphics());
paint(g);
} catch (HeadlessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (AWTException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private Graphics recursiveDraw(BufferedImage img, Graphics imgG) {
updateScale(++recurseCount);
float newWidth = scale*width;
float newHeight = scale*height;
int w = (int) newWidth;
int h = (int) newHeight;
System.out.println("W: " + w + "; H: " + h);
if (w >= 10 && h >= 10) {
//scale image
System.out.print("Creating scaled Image...");
Image scaled = img.getScaledInstance(w, h, Image.SCALE_SMOOTH);
BufferedImage resized = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
imgG = resized.createGraphics();
imgG.drawImage(scaled, 0, 0, null);
System.out.println("...Image drawn to graphics");
//return new graphics
return recursiveDraw(resized, imgG);
} else {
//otherwise return old graphics
System.out.println("Completed.");
return imgG;
}
}
private void updateScale(int count) {
for (int i=0; i<count; i++) {
scale *= $scale;
}
System.out.println("Updated scale: " + scale + "; Recurse count: " + recurseCount);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new ScreenCapture().setVisible(true);
}
});
}
private class LocalWindowListener extends WindowAdapter {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0); return;
}
}
}
EDIT:
This is what I tried after #andrew-thompson 's answer:
ScreenCapture() {
try {
screenCapture = new Robot().createScreenCapture(
new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()) );
height = screenCapture.getHeight();
width = screenCapture.getWidth();
setSize(new Dimension(width, height));
addWindowListener(new LocalWindowListener());
setLayout(new GridLayout());
add(new PaintPanel());
} catch (HeadlessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (AWTException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private class PaintPanel extends JPanel {
#Override
public void paintComponent(Graphics g) {
g=recursiveDraw(screenCapture, g);
//what to do with g?
}
}
I still have the same problem where I don't know how to make the BufferedImage paint to the graphics.

would separate out your Swing code from your recursive image creation code. In fact consider creating a static method that creates and returns the BufferedImage and that has no Swing code in it. Then have your GUI call the method when it wishes, and take the image and either write it to disk or display it in a JLabel's ImageIcon.
When I did this (today in fact), I created a recursive method with this signature
private static void recursiveDraw(BufferedImage img, Graphics imgG, double scale) {
and with this method body (in pseudo-code)
start recursiveDraw method
// most important: all recursions must have a good ending condition:
get img height and width. If either <= a min, return
create a BufferedImage, smlImg, for the smaller image using the height,
width and scale factor
Get the Graphics object, smlG, from the small image
Use smlG.drawImage(...) overload to draw the big image in shrunken
form onto the little image
recursively call recursiveDraw passing in smlImg, smlG, and scale.
dispose of smlG
draw smlImg (the small image) onto the bigger one using the bigger's
Graphics object (passed into this method) and a different
overload of the drawImage method.
end recursiveDraw method
This algorithm resulted in images like:
For example:
import java.awt.*;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class RecursiveDrawTest {
private static final Color BACKGRND_1 = Color.green;
private static final Color BACKGRND_2 = Color.MAGENTA;
private static final Color FOREGRND_1 = Color.blue;
private static final Color FOREGRND_2 = Color.RED;
private static void createAndShowGui() {
final JPanel mainPanel = new JPanel(new BorderLayout());
final JSlider slider = new JSlider(50, 90, 65);
slider.setMajorTickSpacing(10);
slider.setMinorTickSpacing(5);
slider.setPaintLabels(true);
slider.setPaintTicks(true);
JPanel southPanel = new JPanel();
southPanel.add(new JLabel("Percent Size Reduction:"));
southPanel.add(slider);
southPanel.add(new JButton(new AbstractAction("Create Recursive Image") {
#Override
public void actionPerformed(ActionEvent arg0) {
try {
double scale = slider.getValue() / 100.0;
BufferedImage img = createRecursiveImg(scale);
ImageIcon icon = new ImageIcon(img);
JLabel label = new JLabel(icon);
Window win = SwingUtilities.getWindowAncestor(mainPanel);
JDialog dialog = new JDialog(win, "Image", ModalityType.MODELESS);
dialog.getContentPane().add(label);
dialog.pack();
dialog.setLocationRelativeTo(null);
dialog.setVisible(true);
} catch (AWTException e) {
e.printStackTrace();
}
}
}));
mainPanel.add(new JScrollPane(new JLabel(new ImageIcon(createLabelImg()))),
BorderLayout.CENTER);
mainPanel.add(southPanel, BorderLayout.PAGE_END);
JFrame frame = new JFrame("RecursiveDrawTest");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
// create a background image to display in a JLabel so that the GUI
// won't be boring.
private static BufferedImage createLabelImg() {
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
int width = (5 * d.width) / 6;
int height = (5 * d.height) / 6;
BufferedImage img = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = img.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setPaint(new GradientPaint(0, 0, BACKGRND_1, 40, 40, BACKGRND_2, true));
g2.fillRect(0, 0, width, height);
g2.setPaint(new GradientPaint(0, height, FOREGRND_1, 40, height - 40, FOREGRND_2, true));
g2.fillOval(0, 0, 2 * width, 2 * height);
g2.dispose();
return img;
}
// non-recursive image to get the initial image that will be drawn recursively
public static BufferedImage createRecursiveImg(double scale) throws AWTException {
Robot robot = new Robot();
Dimension screenSz = Toolkit.getDefaultToolkit().getScreenSize();
Rectangle screenRect = new Rectangle(screenSz);
BufferedImage img = robot.createScreenCapture(screenRect);
Graphics g = img.getGraphics();
recursiveDraw(img, g, scale); // call recursive method
g.dispose();
return img;
}
// recursive method to draw image inside of image
private static void recursiveDraw(BufferedImage img, Graphics g, double scale) {
int w = img.getWidth();
int h = img.getHeight();
int smlW = (int)(w * scale);
int smlH = (int)(h * scale);
// criteria to end recursion
if (smlW <= 1 || smlH <= 1) {
return;
}
BufferedImage smlImg = new BufferedImage(smlW, smlH, BufferedImage.TYPE_INT_ARGB);
Graphics smlG = smlImg.getGraphics();
// draw big image in little image, scaled to little image
smlG.drawImage(img, 0, 0, smlW, smlH, null);
// recursive call
recursiveDraw(smlImg, smlG, scale);
smlG.dispose(); // clear resources when done with them
// these guys center the smaller img on the bigger
int smlX = (w - smlW) / 2;
int smlY = (h - smlH) / 2;
// draw small img on big img
g.drawImage(smlImg, smlX, smlY, smlW, smlH, null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

Graphics g = recursiveDraw(screenCapture, getGraphics());
Don't call getGraphics(). Override paint(Graphics)1 & use the supplied Graphics instance.
When using Swing, it is actually best to override the paintComponent(Graphics) method of a JComponent or JPanel. Then add that to the top-level container.

Is this what you are hoping for :
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.*;
public class CaptureScreen extends JPanel
{
private BufferedImage screenShot;
private JLabel imageLabel;
private BufferedImage secondScreenShot;
public void createAndDisplayGUI()
{
JFrame frame = new JFrame("CAPTURE SCREEN");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationByPlatform(true);
//imageLabel = new JLabel();
//getImageForLabel();
//add(imageLabel);
frame.getContentPane().add(this);
frame.setSize(600, 600);
frame.setVisible(true);
}
private void getImageForLabel()
{
Robot robot = null;
try
{
robot = new Robot();
}
catch(Exception e)
{
e.printStackTrace();
}
screenShot = robot.createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
ImageIcon icon = new ImageIcon(screenShot);
imageLabel.setIcon(icon);
}
public void paintComponent(Graphics g)
{
Robot robot = null;
try
{
robot = new Robot();
}
catch(Exception e)
{
e.printStackTrace();
}
screenShot = robot.createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
secondScreenShot = getScaledImage((Image) screenShot, 300, 300);
g.drawImage(screenShot, 0, 0, null);
g.drawImage(secondScreenShot, 150, 150, null);
}
private BufferedImage getScaledImage(Image srcImg, int w, int h)
{
BufferedImage resizedImg = new BufferedImage(w, h, BufferedImage.TRANSLUCENT);
Graphics2D g2 = resizedImg.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2.drawImage(srcImg, 0, 0, w, h, null);
g2.dispose();
return resizedImg;
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new CaptureScreen().createAndDisplayGUI();
}
});
}
}
Here is the output :

Get rid of the recursion. Create a single buffered image of the correct size and create a Graphics object for it. Just use a loop to draw progressively smaller scaled images down to whatever threshold you choose. Finally use g.drawImage() inside paintComponent() to draw your image to the screen. If you keep the recursion you need to pass the image and continually overlay the scaled down image. You do not need to return anything from the method.

Component with transparent background to BufferedImage?

I have a component extends JPanel. It saves itself as bufferedimage on every call of paintComponent method. Component is not completely transparent, only its background. Problem is background is not transparent. I am using setOpaque(false);
Here is my relevant code;
private BufferedImage bufImage = null;
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
// if first time call
if (bufImage == null) {
int w = this.getWidth();
int h = this.getHeight();
bufImage = (BufferedImage)this.createImage(w, h);
}
g2.drawImage(bufImage, null, 0, 0);
// draw sth
g2.draw(sth);
}
--
I also tried
bufImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
instead of
bufImage = (BufferedImage)this.createImage(w, h);
When i do that; background transperancy works but i can only draw with white color. I have no idea what causes that.
Note:
I used that code to check if it is working;
File outputfile = new File("saved.png");
ImageIO.write(bufImage, "png", outputfile);
saved.png had transparent background but drawings were only white.
This is the component, only lets drawing rectangle with mouse;
class PaintPanel extends JPanel implements MouseListener, MouseMotionListener {
private BufferedImage _bufImage = null;
private boolean dragging = false;
private Point _start = null, _end = null;
public PaintPanel() {
setOpaque(false);
this.addMouseListener(this);
this.addMouseMotionListener(this);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
if (_bufImage == null) {
int w = this.getWidth();
int h = this.getHeight();
_bufImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
//_bufImage = (BufferedImage)this.createImage(w, h);
}
g2.drawImage(_bufImage, null, 0, 0);
if (dragging) {
drawCurrentShape(g2);
}
}
private void drawCurrentShape(Graphics2D g2) {
int startx = (int) _start.getX();
int starty = (int) _start.getY();
int stopx = (int) _end.getX();
int stopy = (int) _end.getY();
int width = Math.abs(startx - stopx);
int height = Math.abs(starty - stopy);
int x = startx, y = starty;
if(x > stopx)
x = stopx;
if(y > stopy)
y = stopy;
Rectangle r = new Rectangle(x, y, width, height);
g2.draw(r);
}
public void mousePressed(MouseEvent e) {
dragging = true;
_start = e.getPoint();
_end = _start;
}
public void mouseDragged(MouseEvent e) {
_end = e.getPoint();
this.repaint();
}
public void mouseReleased(MouseEvent e) {
_end = e.getPoint();
if (dragging) {
dragging = false;
drawCurrentShape(_bufImage.createGraphics());
this.repaint();
}
}
public void mouseMoved (MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited (MouseEvent e) {}
public void mouseClicked(MouseEvent e) {}
}

try this:
bufImage = new BufferedImage(w,h,java.awt.image.BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = bufImage.createGraphics();
this.print(graphics);
graphics.dispose();
The key is to use print()
Edit: I tried the following and transparency works like a charm:
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test2 {
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel p = new JPanel();
p.setPreferredSize(new Dimension(400, 400));
p.setOpaque(false);
JButton button = new JButton("Hello world");
p.add(button);
frame.add(p);
frame.pack();
frame.setVisible(true);
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
BufferedImage bufImage = new BufferedImage(p.getWidth(), p.getHeight(), java.awt.image.BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = bufImage.createGraphics();
p.print(graphics);
graphics.dispose();
try {
ImageIO.write(bufImage, "png", new File("d:/tmp/tmp.png"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}

createImage(w, h) will create a "blank" image with the specified width and height. That being said, what you'll need to do is invoke createGraphics on the BufferedImage instance and draw directly to the returned Graphics object.

Convert a Graphics2D to an Image or BufferedImage

I have a little problem here.
I have an applet, where user can "draw" inside it. To do that, I use the java.awt.Graphics2D.
But, how can I do to save the user draw image as a JPEG image, or at least, convert it to a BufferedImage or something? I don't know how to do that.
Thanks.

Have them draw directly in a BufferedImage by way of it's Graphics2D object which you can get via getGraphics(). Then use ImageIO.write(...) to output the image to whatever file type you desire (and that's supported). The ImageIO API should help you with this: ImageIO API.
The other issue you'll have is where are they supposed to save the image once it has been drawn? On their own computer? If so and this is an applet program, then the applet will need to be "signed" in order for it to have the permission to write to disk. If you're unsure on this, check out Google, this article, or you may wish to write a new question for this issue alone.
Edit 1: code example
For example:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
#SuppressWarnings("serial")
public class DrawAndSaveImage extends JPanel {
private static final int BI_WIDTH = 600;
private static final int BI_HEIGHT = BI_WIDTH;
private static final Color LABEL_DRAW_COLOR = new Color(180, 180, 255);
private static final Stroke LABEL_DRAW_STROKE = new BasicStroke(1);
private static final Stroke BIMAGE_DRAW_STROKE = new BasicStroke(4);
private static final int COLOR_DIV = 5;
private BufferedImage bImage = new BufferedImage(BI_WIDTH, BI_HEIGHT,
BufferedImage.TYPE_INT_RGB);
private List<Point> pointList = new ArrayList<Point>();
private JLabel imageLabel;
private List<Color> colorList = new ArrayList<Color>();
private Random random = new Random();
public DrawAndSaveImage() {
Graphics2D g2d = bImage.createGraphics();
g2d.setBackground(Color.white);
g2d.clearRect(0, 0, BI_WIDTH, BI_HEIGHT);
g2d.dispose();
for (int r = 0; r < COLOR_DIV; r++) {
for (int g = 0; g < COLOR_DIV; g++) {
for (int b = 0; b < COLOR_DIV; b++) {
Color c = new Color((r * 255) / COLOR_DIV,
(g * 255) / COLOR_DIV, (b * 255) / COLOR_DIV);
colorList.add(c);
}
}
}
imageLabel = new JLabel(new ImageIcon(bImage)) {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
paintInLabel(g);
}
};
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
imageLabel.addMouseListener(myMouseAdapter);
imageLabel.addMouseMotionListener(myMouseAdapter);
imageLabel.setBorder(BorderFactory.createEtchedBorder());
JButton saveImageBtn = new JButton("Save Image");
saveImageBtn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
saveImageActionPerformed();
}
});
JButton clearImageBtn = new JButton("Clear Image");
clearImageBtn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Graphics2D g2 = bImage.createGraphics();
g2.setBackground(Color.white);
g2.clearRect(0, 0, BI_WIDTH, BI_HEIGHT);
g2.dispose();
imageLabel.repaint();
}
});
JPanel btnPanel = new JPanel();
btnPanel.add(saveImageBtn);
btnPanel.add(clearImageBtn);
setLayout(new BorderLayout());
add(imageLabel, BorderLayout.CENTER);
add(btnPanel, BorderLayout.SOUTH);
}
private void saveImageActionPerformed() {
JFileChooser filechooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter(
"JPG Images", "jpg");
filechooser.setFileFilter(filter);
int result = filechooser.showSaveDialog(this);
if (result == JFileChooser.APPROVE_OPTION) {
File saveFile = filechooser.getSelectedFile();
try {
ImageIO.write(bImage, "jpg", saveFile);
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void paintInLabel(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(LABEL_DRAW_COLOR);
g2d.setStroke(LABEL_DRAW_STROKE);
if (pointList.size() < 2) {
return;
}
for (int i = 1; i < pointList.size(); i++) {
int x1 = pointList.get(i - 1).x;
int y1 = pointList.get(i - 1).y;
int x2 = pointList.get(i).x;
int y2 = pointList.get(i).y;
g2d.drawLine(x1, y1, x2, y2);
}
}
private class MyMouseAdapter extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
pointList.add(e.getPoint());
imageLabel.repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
Graphics2D g2d = bImage.createGraphics();
g2d.setColor(colorList.get(random.nextInt(colorList.size())));
g2d.setStroke(BIMAGE_DRAW_STROKE);
if (pointList.size() >= 2) {
for (int i = 1; i < pointList.size(); i++) {
int x1 = pointList.get(i - 1).x;
int y1 = pointList.get(i - 1).y;
int x2 = pointList.get(i).x;
int y2 = pointList.get(i).y;
g2d.drawLine(x1, y1, x2, y2);
}
}
g2d.dispose();
pointList.clear();
imageLabel.repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
pointList.add(e.getPoint());
imageLabel.repaint();
}
}
private static void createAndShowUI() {
JFrame frame = new JFrame("DrawAndSaveImage");
frame.getContentPane().add(new DrawAndSaveImage());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}

I do it that way, and works very well:
BufferedImage awtImage = new BufferedImage(drawPanel.getWidth(), drawPanel.getHeight(), BufferedImage.TYPE_INT_RGB);
Graphics g = awtImage.getGraphics();
drawPanel.printAll(g);
try
{
String caminhoImagem = System.getProperty("user.home") + "\\temps\\assinatura.jpg";
FileOutputStream fos = new FileOutputStream(caminhoImagem);
JPEGImageEncoderImpl j = new JPEGImageEncoderImpl(fos);
j.encode(awtImage);
fos.close();
} catch(e) {..... }
That's all :)
Thanks everyone :)

Use the drawImage method provided by Graphics2D and write it using ImageIO
BufferedImage img;
g2dObject.drawImage(img, null, 0, 0);
ImageIO.write(img, "JPEG", new File("foo.jpg"));

Use the "drawOnImage" example from Custom Painting Approaches. Then to create the image of the panel you can use the Screen Image class.

If you'd like to draw JComponent's image onto BufferedImage (JApplet extends JComponent):
JComponent whatToDraw = ...;
BufferedImage img = new BufferedImage(whatToDraw.getWidth(),
whatToDraw.getHeight(), BufferedImage.TYPE_INT_RGB);
whatToDraw.printAll(img.getGraphics());
And to write its data to JPEG file:
ImageIO.write(img, "jpg", new File("something.jpg"));