Develop Reference

Java Swing image cut off/zoomed

when I try to render a png image in Java Swing, it is cut off/zoomed on all sides. Here is my code:
this.setSize(500, 500);
this.setResizable(false);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
this.getGraphics().drawImage(getImage("IMAGE PATH"), 0, 0, this);
And this is my getImage function
public static Image getImage(String path) {
File file = new File(path);
try {
return ImageIO.read(file);
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
The image I want to render is 500x500, just like my frame, but it still comes out wrong. This also applies to when I use the function like this:
Image image = getImage("Image Path");
assert image != null;
JLabel picLabel = new JLabel(new ImageIcon(image));
Here is one of the images I am trying to render:
Here is the outcome:
It is kind of hard to tell from this example, but the ground should be lower and the trees higher.

Don't set the size of the frame
If your image is 500x500 then how can you expect the image size and frame size to be the same when the frame also has a title bar and borders?
Don't do custom painting`
Instead:
create a JLabel with an ImageIcon.
Add the label to the frame
invoke pack() before making the frame visible.
All the components will get the proper size.
Read the Swing tutorial on How to Use Labels for more information and examples.

Even though #camikr found a solution, I found a better one for my needs.
What I did, was I created a new JPanel and ran setPreferredSize with the dimensions of my JFrame (500x500). Then I overrided the paintComonent function to render the image using the Graphics2D class.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.util.Objects;
public class MyPanel extends JPanel {
public Image loadedImage = getImage("Image");
public LoadState() {
setPreferredSize(new Dimension(500,500));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.drawImage(loadedImage, 0, 0, null);
g2.dispose();
}
}
EDIT: Fix what #Harald K suggested

repaint() call from the constructor

I'm trying to display loaded resource-image.
And it works, but only after user resized the window.
import javax.swing.*; import java.awt.*;
class MyMainWindow extends JFrame{
Image img;
public MyMainWindow(){
setSize(300,300);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
img = MyResourceLoader.getImage("res.jpg");
repaint();
setVisible(true);
}
#Override
public void paint (Graphics g){
super.paint(g);
if (img != null)
g.drawImage(img, 0,0, null);
}
}
public class ResourcesProgram {
public static void main(String[] args) {
new MyMainWindow();
}
}
Why the constructor's repaint() call doesn't work?
And what should I do to show this image from the start?
Resource Loader class:
import java.awt.*;
public class MyResourceLoader{
static MyResourceLoader rl = new MyResourceLoader();
static public Image getImage(String fileName){
return Toolkit.getDefaultToolkit().getImage(rl.getClass().getResource("images/" + fileName));
}
}

Okay, so a bunch of things...
First...
Because the window has not yet been realised on the screen (attached to a native peer), there is nothing for repaint to paint...
Second...
Toolkit.getDefaultToolkit().getImage(rl.getClass().getResource("images/" + fileName));
Passes the actually loading of the image to a background thread, meaning that while you get a non-null value returned, the actual image data might not have been fully loaded.
You should consider using ImageIO.read instead, it will only return AFTER the image data has been fully loaded and will also throw an exception if something goes wrong (unlike Toolkit.getImage). See Reading/Loading an Image for more details...
Third...
All Swing components implement the ImageObserver interface, this means when you call Graphics#drawImage, you should pass the object as the ImageObserver parameter
g.drawImage(img, 0,0, this);
This allows the component to monitor updates from the loading of the image and reschedule repaint as required.
Fourth...
You should avoid overriding paint of top level containers, apart from not been double buffered, there is a bunch of components between the frame and the user, which can interfere with the painting process.
Instead, you should extend from something like JPanel and override it's paintComponent method, performing your custom painting there. You should then add this panel to an instance of JFrame (or some other component as needed)
Take a look at Painting in AWT and Swing and Performing Custom Painting for more details
Fifth...
You should be making sure that you create and modify your UI only from within the context of the Event Dispatching Thread, see Initial Threads for more details

Paint is immediately called when the code is initialized. To see this, get rid of repaint(); in your constructor, and add in your paint method, g.drawLine(0, 0, 300, 300);

Try this, you may have to add some imports:
import javax.swing.*; import java.awt.*;
class MyMainWindow extends JFrame{
Image img;
public MyMainWindow(){
setSize(300,300);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
img = MyResourceLoader.getImage("res.jpg");
setVisible(true);
}
#Override
public void paint (Graphics g){
super.paint(g);
if (img != null)
g.drawImage(img, 0,0, this);
}
}
public class ResourcesProgram {
public static void main(String[] args) {
new MyMainWindow();
}
}
Resource Loader:
import javax.swing.*; import java.awt.*;
public class MyResourceLoader {
public static Image getImage(String fileName){
ImageIcon icon = new ImageIcon(getClass().getResource(fileName));
return icon.getImage();
}
}

setting a JFrame background, why this doesn't work?

I want to set a background to my jFrame, and I'm using this code:
import java.awt.Graphics;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class DemoBackgroundSwing extends JPanel {
private Image img;
public DemoBackgroundSwing() {
System.out.println("done");
img = Toolkit.getDefaultToolkit().createImage("red.png");
System.out.println("done");
loadImage(img);
System.out.println("done");
}
private void loadImage(Image img) {
try {
MediaTracker track = new MediaTracker(this);
track.addImage(img, 0);
track.waitForID(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
protected void paintComponent(Graphics g) {
setOpaque(false);
System.out.println("done");
g.drawImage(img, 0, 0, null);
super.paintComponent(g);
}
public static void main(String... argv) {
JFrame frame = new JFrame("Demo Background Image");
DemoBackgroundSwing back = new DemoBackgroundSwing();
System.out.println("done");
frame.getContentPane().add(back);
frame.setSize(400, 287);
frame.setVisible(true);
}
}
when I execute it, in system out I have 5 "done". so this means that all tasks are executed.
I don't understand where's the error. Please Help me!

Print the width of loaded image if it's -1 then image is not properly loaded.
img = Toolkit.getDefaultToolkit().createImage("red.png");
System.out.println(img.getWidth(null)); // check what it prints
It's worth reading Java Tutorial on Loading Images Using getResource
You can try any one based on image location.
// Read from same package
ImageIO.read(getClass().getResourceAsStream("c.png"));
// Read from images folder parallel to src in your project
ImageIO.read(new File("images/c.jpg"));
// Read from src/images folder
ImageIO.read(getClass().getResource("/images/c.png"))
// Read from src/images folder
ImageIO.read(getClass().getResourceAsStream("/images/c.png"))
Read more...
Some Points:
call super.paintComponent(g); at first line in the overridden paintComponent() method.
Use ImageIO instead of Toolkit to load the image.
Use frame.pack() instead of frame.setSize() that fits the components as per component's preferred size.
Override getPreferredSize() to set the preferred size of the JPanel in case of custom painting.
Use SwingUtilities.invokeLater() or EventQueue.invokeLater() to make sure that EDT is initialized properly.
Read more
Why to use SwingUtilities.invokeLater in main method?
SwingUtilities.invokeLater
Should we use EventQueue.invokeLater for any GUI update in a Java desktop application?

Is there ever a reason drawImage won't actually draw an image?

private void renderLevelBackground(Graphics2D g2) {
Image backgroundImage = model.getBackgroundImage();
g2.drawImage(backgroundImage, 0, 0, null);
}
This is my code, I know that the backgroundImage is loaded properly because if I getWidth/Height it gives me the correct values. Is there anyway to test if it's the image or if it's the method somehow? It just won't draw on my screen despite the fact that I've used the drawImage method many times in this project already, all of which work flawlessly.
Thanks

"Is there ever a reason drawImage won't actually draw an image?"
Possibility, there is no image due to a bad path provided. Use ImageIO.read() which will cause an exception if the image file is not found. For example
public class ImagePanel extends JPanel {
private BufferedImage image;
public ImagePanel() {
try {
image = ImageIO.read(getClass().getResource("/resources/image.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
If the image is not found, it will throw an IO exception.
Possibility, the panel to which you are drawing, has no preferred size (0 x 0), and you are adding it a container wit layout that respects preferred sizes, so the ImagePanel will not be able to show the image. For example
public class ImagePanel extends JPanel {
protected void paintComponent(...) {
...
}
JPanel panel = new JPanel(); // default FlowLayout that respects preferred sizes
panel.add(new ImagePanel());
To fix this, you can override the gerPreferredSize() of the ImagePanel
public class ImagePanel extends JPanel {
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
}
Possibility, you are not calling your method within the graphics context of the paint[Component] method.
protected void paintComponent(Graphics 2d) {
super.paintComponent(g);
Grapchics2D g2 = (Graphics2D)g;
renderLevelBackground(g2);
}
Other than that, these are all just guesses, and you should provide some more code code (preferably an MCVE) to help us better help you with the problem.
Possible Alternative to your approach. It seems like (from the little code snippet and it method signature semantics) you want to change the background image, when a level have changed. Consider using setBackgroundImage(BufferedImage image) method in your panel class, when the image is drawn. You can then set the background, whenever need be. Something like
public class BackgroundPanel extends JPanel {
private BufferedImage backgroundImage;
public void setBackgroundImage(BufferedImage image) {
this.backgroundImage = image;
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Grpahics2D g2 = (Graphics2D)g;
if (image != null) {
g2.drawImage(backgroundImage, 0, 0, this);
}
}
}
So whenever you call setBackgroundImage, the image will change, and be repainted.

You may need to explicitly tell the JComponent that you are painting onto that it needs to be redrawn with revalidate() and repaint()

How do i have a background image resize in a java gui?

So im making a gui, and i have a background image for it. i dont know how to make it set as the background, so any help with that would be good. an explination would also be good. also, after we get that image as a background, how do we get the image resize to the size of the window. such as
image.setSize(frame.getHeight(), frame.getWidth());
but i dont know if that would work. the image name is ABC0001.jpg and the frame name is frame. thanks!

To get the image to resize, you can either use
public void paintComponent(Graphics g) {
g.drawImage(img, 0, 0, getWidth(), getHeight(), this); // draw the image
}
or you can use a componentlistener, implemented like:
final Image img = ...;
ComponentListener cl = new ComponentAdapter() {
public void componentResized(ComponentEvent ce) {
Component c = ce.getComponent();
img = im1.getScaledInstance(c.getWidth(), c.getHeight(), Image.SCALE_SMOOTH);
}
};
Image quality will degrade over time with the second solution, so it is recommended that you keep the original and the copy separate.

Create a class the extends JPanel. Have that class load the image by overriding paintComponent
class BackgroundPanel extends JPanel
{
Image img;
public BackgroundPanel()
{
// Read the image and place it in the variable img so it can be used in paintComponent
img = Toolkit.getDefaultToolkit().createImage("ABC0001.jpg");
}
public void paintComponent(Graphics g)
{
g.drawImage(img, 0, 0, null); // draw the image
}
}
Now that you have this class, simply add this to your JFrame (or whereever you want the background).
//create refrence if you want to add stuff ontop of the panel
private BackgroundPanel backGroundPanel;
//constructor
add(backGroundPanel, BorderLayout.CENTER);
The size of the background will fill the entire frame so no need to scale it unless you want it smaller