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java BufferedImage looses quality

In the following code, two lines are being drawn on the left side of the JFrame using the paintComponent method of a JLabel. The program also runs a method, which creates a BufferedImage with both lines painted on to it. The BufferedImage is then painted on to the right side of the screen. The method, which creates the BufferedImage follows the same procedure as the paintComponent method, however it is pretty clear that the BufferedImage looses a substantial amount of quality compared to the paintComponent method.
package pack;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Test extends JFrame{
private static final long serialVersionUID = 1L;
BufferedImage img = new BufferedImage(250, 500, BufferedImage.TYPE_4BYTE_ABGR);
public Test() {
convertToImage();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(700, 700);
setVisible(true);
setContentPane(new label());
}
public class label extends JLabel {
private static final long serialVersionUID = 1L;
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.BLACK);
g2d.drawLine(100, 100, 250, 250);
g2d.drawLine(150, 350, 150, 500);
g2d.drawImage(img, 300, 0, 250, 500, null);
}
}
public void convertToImage() {
BufferedImage image = img;
Graphics2D g2d = image.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.BLACK);
g2d.drawLine(100, 100, 250, 250);
g2d.drawLine(150, 350, 150, 500);
img = image;
}
public static class Main {public static void main(String[] args) {new Test();}}
}

How do you create a gradient for JPanel? Also, how do you call a class within a class in Java?

I am making a Java GUI and I have searched the internet for 2 hours on how make a gradient for a JPanel. The code below is that I have, but when run the gradient does not show. What is wrong?
I've tried many other posts from similar questions on this throughout the Internet but they don't work. I've tried numerous versions, but I also don't exactly know how to run a class within a class. Can someone help me please?
class TestPanel extends JPanel{
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
int w = getWidth();
int h = getHeight();
Color color1 = Color.BLUE;
Color color2 = Color.GREEN;
GradientPaint gp = new GradientPaint(0, 0, color1, 0, h, color2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
}
} //this is nested within the main class
//some code
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
CreateGUI cg = new CreateGUI();
cg.create(); //previous method (not mentioned here)
CreateGUI.TestPanel tp = cg.new TestPanel(); //problem
JPanel panel = new JPanel();
f.add(panel);
f.setSize(800, 600);
f.setLocationRelativeTo(null);
f.getContentPane().setLayout(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
});
}
I expect there to be a gradient but there is none; the background of the JPanel is still white

The instance of TestPanel is never added to anything
null layouts will prevent the component from been sized and positioned, so you won't see anything even if your did the previous step
You should, unless you're adding child components to it, provide a sizing hint, so that the layout managers have something to work with.
For example:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
class TestPanel extends JPanel {
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
int w = getWidth();
int h = getHeight();
Color color1 = Color.BLUE;
Color color2 = Color.GREEN;
GradientPaint gp = new GradientPaint(0, 0, color1, 0, h, color2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
g2d.dispose();
}
}
}

Creating a JLabel with a Gradient

I'm new to Java and I'm trying to create a heading using a JLabel and for its fill to be a gradient. I cannot get it to work and I've been trying for a while. I've been grabbing bits of come from here and other websites and cannot seem to make this work, nor make sense of other peoples more complex code that does work. Here are my two classes so far:
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EtchedBorder;
public class Test {
public static void main(String[] args) {
new Test().setupGUI();
}
public void setupGUI() {
//set up frames and buttons etc.
JFrame theFrame = new JFrame ("Crystal Ball");
theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel background = new JPanel();
background.setBackground(Color.BLUE);
background.setLayout(new BoxLayout(background, BoxLayout.PAGE_AXIS));
theFrame.setSize(500,1000);
DLabel heading = new DLabel("Guess a Number");
heading.setText("GUESS A NUMBER");
heading.setPreferredSize(new Dimension(theFrame.getWidth(),100));
heading.setFont(new Font("Serif", Font.PLAIN, 40));
heading.setAlignmentX(Component.CENTER_ALIGNMENT);
//heading.setBackground(Color.YELLOW);
heading.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.RAISED));
background.add(heading);
theFrame.getContentPane().add(background);
theFrame.pack();
theFrame.setVisible(true);
//startGame();
}
}
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.BorderFactory;
import javax.swing.JLabel;
public class DLabel extends JLabel
{
Dimension size = new Dimension(70, 80);
public DLabel(String name)
{
this.setPreferredSize(size);
this.setText(name);
this.setBorder(BorderFactory.createBevelBorder(TOP, Color.white, Color.black));
this.setOpaque(true);
}
public void paintComponent(Graphics g) {
// super.paintComponent(g); // *** commented
Graphics2D g2d = (Graphics2D) g;
Color color1 = Color.YELLOW;
Color color2 = color1.brighter();
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(0, 0, color1, 0, h, color2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
super.paintComponent(g); // *** added
}
}

There is one little "trick" you can actually do, by leaving the label transparent, you can actually paint under the text by painting BEFORE you call super.paintComponent, for example...
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.LinearGradientPaint;
import java.awt.Point;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestLabel101 {
public static void main(String[] args) {
new TestLabel101();
}
public TestLabel101() {
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);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JLabel {
public TestPane() {
setText("Happy, Happy");
setForeground(Color.WHITE);
setHorizontalAlignment(CENTER);
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
LinearGradientPaint lgp = new LinearGradientPaint(
new Point(0, 0),
new Point(0, getHeight()),
new float[]{0.142f, 0.284f, 0.426f, 0.568f, 0.71f, 0.852f, 1f},
new Color[]{Color.PINK, Color.MAGENTA, Color.BLUE, Color.GREEN, Color.YELLOW, Color.ORANGE, Color.RED});
g2d.setPaint(lgp);
g2d.fill(new Rectangle(0, 0, getWidth(), getHeight()));
g2d.dispose();
super.paintComponent(g);
}
}
}
nb: I should point out that this process is inefficient, as the RepaintManager will still want to paint under the component
There is another trick, but my two year old daughter wants to check to see if Santa is here ;)
Updated
The other trick involves understanding how the paint process actually works. When you call super.paintComponent, it calls the update method on the ComponentUI (look and feel delegate), this is actually the method that fills the background if the component is opaque, this method then calls the look and feels delegate's paint method, which actually does the base painting...
We can circumvent the process slightly and instead of calling super.paintComponent, we can call the look and feels delegate's paint method directly...
public class TestPane extends JLabel {
public TestPane() {
setText("Happy, Happy");
setForeground(Color.WHITE);
setHorizontalAlignment(CENTER);
setOpaque(true);
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
LinearGradientPaint lgp = new LinearGradientPaint(
new Point(0, 0),
new Point(0, getHeight()),
new float[]{0.142f, 0.284f, 0.426f, 0.568f, 0.71f, 0.852f, 1f},
new Color[]{Color.PINK, Color.MAGENTA, Color.BLUE, Color.GREEN, Color.YELLOW, Color.ORANGE, Color.RED});
g2d.setPaint(lgp);
g2d.fill(new Rectangle(0, 0, getWidth(), getHeight()));
g2d.dispose();
getUI().paint(g, this);
}
}
This is more efficient then the previous example, as it doesn't require the RepaintManager to paint the area underneath this component, but it might not work with all look and feels

The problem is that you made the JLabel opaque, which means it will paint the background. So the call to super.paintComponent(...) over paints the gradient background. So get rid of:
//this.setOpaque(true);
Another problem with the code is that color1.brighter() doesn't work. Try something like:
Color color2 = Color.RED;
Also, You should not change the Graphics object, since that object is also used to paint other Swing components. Instead you should use g.create() to get a copy of the Graphics object. Make your changes to that object, do the painting and then dispose() the object.
So the (untested) code would be something like:
Graphics2D g2d = (Graphics2D)g.create();
...
g2d.fillRect(...);
g2d.dispose();
super.paintCompoenent(g);

You should set your gradientPaint object to your Graphics and then pass that into super.paintComponent
try this:
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
Color color1 = Color.YELLOW;
Color color2 = color1.brighter();
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(0, 0, color1, 0, h, color2);
g2d.setPaint(gp);
super.paintComponent(g2d);
}

How to disable java.awt.Graphics.fillRect(int x, int y, int width, int height)'s effect?

It's the original image:
I use java.awt.Graphics.fillRect(int x, int y, int width, int height) to add a coloured rectangle on the image.
Graphics imageGraphics = image.createGraphics();
Color color = new Color(0,0,0,100);
imageGraphics.setColor(color);
imageGraphics.fillRect(0, 0, 800, 600);
So the image has been inverted and looks like this:
After that,I want to clear the black transparent rectangle partly and show the original image.
imageGraphics.clearRect(100,100,100,100);
But the effect is like this:
What my requirement is:
I want to know why it doesn't work and is there any other way to realize it?

Remember, painting is destructive. It might be possible to use AlphaComposite to achieve this result, but a simpler solution might be to simple constructive a compound shape and paint that instead.
The following example creates two Rectangles, one been the area we want to fill and one been the area we want to show, the second is then subtracted from the first (to create the window) and then the result is painted on top of the image
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.Rectangle;
import java.awt.geom.Area;
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.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ShowArea {
public static void main(String[] args) {
new ShowArea();
}
public ShowArea() {
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);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private BufferedImage img;
public TestPane() {
try {
img = ImageIO.read(new File("sample.png"));
Rectangle bounds = new Rectangle(0, 0, img.getWidth(), img.getHeight());
Rectangle clip = new Rectangle(150, 10, 100, 100);
Area area = new Area(bounds);
area.subtract(new Area(clip));
Graphics2D g2d = img.createGraphics();
g2d.setColor(Color.BLACK);
g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
g2d.fill(area);
g2d.dispose();
} catch (IOException ex) {
ex.printStackTrace();
}
}
#Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
int x = (getWidth() - img.getWidth()) / 2;
int y = (getHeight() - img.getHeight()) / 2;
g2d.drawImage(img, x, y, this);
g2d.dispose();
}
}
}
If I were doing some kind of paint program, I would do this all within the paintComponent method or in some way that it didn't effect the original image, otherwise you've basic destroyed the image until you re-load it
Another solution might be to take a copy of the original area you want to keep and repaint it back on top after, for example...
img = ImageIO.read(new File("sample.png"));
// This is the portion of the image we want to save...
BufferedImage cutout = img.getSubimage(150, 10, 100, 100);
// This is the area we want to paint over...
Rectangle bounds = new Rectangle(0, 0, img.getWidth(), img.getHeight());
Graphics2D g2d = img.createGraphics();
g2d.setColor(Color.BLACK);
// Save the current Composite so we can reset it...
Composite comp = g2d.getComposite();
// Apply the composite and fill the area...
g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
g2d.fill(area);
// Reset the composite
g2d.setComposite(comp);
// Draw the part of the image we saved previously...
g2d.drawImage(cutout, 150, 10, this);
g2d.dispose();

You cant do that the way you're trying to.
It can be done by creating a BufferedImage filled with Color(0,0,0,200), then in that image draw rectangle with color Color(0,0,0,200) and then apply it on image.
Remember, that drawing filledRectange is not a "undo operation"- it is written on pixels and it can't be undone.
EDIT
Icon imageIcon = new javax.swing.ImageIcon("image.jpg");
BufferedImage mask = new BufferedImage(imageIcon.getIconWidth(), imageIcon.getIconHeight(), BufferedImage.TYPE_4BYTE_ABGR);
BufferedImage image = new BufferedImage(imageIcon.getIconWidth(), imageIcon.getIconHeight(), BufferedImage.TYPE_4BYTE_ABGR);
imageIcon.paintIcon(null, image.getGraphics(), 0, 0);
Graphics maskGraphics = mask.getGraphics();
//drawing grey background
maskGraphics.setColor(new Color(0, 0, 0, 120));
maskGraphics.fillRect(0, 0, mask.getWidth(), mask.getHeight());
//drawing black frame
maskGraphics.setColor(new Color(0, 0, 0, 255));
maskGraphics.drawRect(99, 99, 301, 301);
//drawing original image window
maskGraphics.drawImage(image, 100, 100, 400, 400, 100, 100, 400, 400, null);
//apply mask on image
new ImageIcon(mask).paintIcon(null, image.getGraphics(), 0, 0);
//result presentation
label.setIcon(new ImageIcon(image));

Yes this is easily doable. The problem is that any draw operation is destructive, what you see is what you get, the information that was painted upon is lost.
Something like this where you store a subimage, do your paint operation then draw the subimage back on top.
public class Q23709070 {
public static void main(String[] args) {
JFrame frame = new JFrame();
Panel p = new Panel();
frame.getContentPane().add(p);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
static class Panel extends JPanel {
int w = 400;
int h = 400;
int x = 100;
int y = 100;
BufferedImage img;
BufferedImage subImg;
BufferedImage save;
public Panel() {
try {
img = ImageIO.read(getClass().getResourceAsStream("0qzCf.jpg"));
} catch (IOException e) {
}
subImg = img.getSubimage(x, y, w, h);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
Color g2dColor = g2d.getColor();
Color fillColor = new Color(0, 0, 0, 100);
g2d.drawImage(img, 0, 0, null);
g2d.setColor(fillColor);
g2d.fillRect(0, 0, img.getWidth(), img.getHeight());
g2d.drawImage(subImg, x, y, null);
g2d.setColor(g2dColor);
if (save == null) {
save = new BufferedImage(img.getWidth(), img.getHeight(),
img.getType());
this.paint(save.getGraphics());
try {
ImageIO.write(save, "jpg", new File("save.jpg"));
} catch (IOException e) {
}
}
}
#Override
#Transient
public Dimension getPreferredSize() {
return new Dimension(img.getWidth(), img.getHeight());
}
}
}
Rendering

What is the simplest way to draw in Java?

What is the simplest way to draw in Java?
import java.awt.*;
import javax.swing.*;
public class Canvas
{
private JFrame frame;
private Graphics2D graphic;
private JPanel canvas;
public Canvas()
{
frame = new JFrame("A title");
canvas = new JPanel();
frame.setContentPane(canvas);
frame.pack();
frame.setVisible(true);
}
public void paint(Graphics g){
BufferedImage offImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Grapics2D g2 = offImg.createGraphics();
g2.setColor(new Color(255,0,0));
g2.fillRect(10,10,200,50);
}
}
This doesn't work and I have no idea how to get anything to appear.

Easiest way:
public class Canvas extends JPanel {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
// painting code goes here.
}
}
You simply need to extend JPanel and override the paintComponent method of the panel.
I'd like to reiterate that you should not be overriding the paint method.
Here is a very minimalistic example that works.
public static void main(String[] args) {
JFrame f = new JFrame();
JPanel p = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(0, 0, 100, 100);
}
};
f.add(p);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}

// No. 1
// Create a graphics context on the buffered image
Graphics2D g2d = bimage.createGraphics();
// Draw on the buffered image
g2d.setColor(Color.red);
g2d.fill(new Ellipse2D.Float(0, 0, 200, 100));
g2d.dispose();
// No.2
// In case the buffered image supports transparency
g2d = bimage.createGraphics();
// Transparency is created on all the filled pixels
Color transparent = new Color(0, 0, 0, 0);
g2d.setColor(transparent);
g2d.setComposite(AlphaComposite.Src);
g2d.fill(new Rectangle2D.Float(20, 20, 100, 20));
g2d.dispose();

To make something appear in paint(Graphics g) you need to call the drawing methods (like fillRect) on that Graphics. You are creating a bitmap and then drawing to the bitmap, not the screen.
public void paint(Graphics g){
g.setColor(new Color(255,0,0));
g.fillRect(10,10,200,50);
}

jjnguy already wrote how to do it right ... but here why it does not work in your example:
import java.awt.*;
import javax.swing.*;
public class Canvas
Here you have a class which does not relate in any way to Swing or AWT.
(By the way, you may want to select another name to avoid confusion with java.awt.Canvas.)
{
private JFrame frame;
private Graphics2D graphic;
private JPanel canvas;
public Canvas()
{
frame = new JFrame("A title");
canvas = new JPanel();
frame.setContentPane(canvas);
Here you are creating a new JPanel (for confusion also named canvas), and add it to the frame.
Is is this panel's paint and paintComponent methods which are called when the system shows your frame.
frame.pack();
frame.setVisible(true);
}
public void paint(Graphics g){
BufferedImage offImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Grapics2D g2 = offImg.createGraphics();
g2.setColor(new Color(255,0,0));
g2.fillRect(10,10,200,50);
}
This paint method is never used at all (since it is not part of a component), and if it would be called, then you are only painting to some BufferedImage, not to the screen.
}