I'm trying to display a small 16x16 pixel image to a JPanel. I've written a simple function that creates and returns a BufferedImage object that I'm then trying to pass to paintComponent, however, nothing is rendering when I launch the program (with no errors being printed to the console). Help?
Thanks!
public BufferedImage loadImage(String filePath) {
BufferedImage img = null;
try {
img = ImageIO.read(new File(filePath));
} catch (IOException e) {
}
return img;
}
public void paintComponent(Graphics g) {
g.drawImage(loadImage("/resources/tile.png"), 0, 0, this);
}
}
we can also use the below source code inside paintComponent to draw an image swing.
public void paintComponent(Graphics g) {
Toolkit t=Toolkit.getDefaultToolkit();
Image image=t.getImage(<path of image>);
g.drawImage(image, 0,0,this);
}
where,
img - the specified image to be drawn. This method does nothing if img is null.
x - the x coordinate.
y - the y coordinate.
observer - object to be notified as more of the image is converted.
in case to load an bufferImage, you can also check the below link contains good amount of details.
https://www.baeldung.com/java-images
Thanks
I have an applet. I set its image background. It works fine.
Now I want to set a background image to a JSlider.
How can I do that?
You will need to create a custom JSlider class and override the paintComponent method. Be sure to call setOpaque(false) on your slider object.
public class CustomSlider extends JSlider
{
private Image img = null;
public CustomSlider()
{
try
{
img = ImageIO.read(new File("background.jpg"));
}
catch (IOException e)
{
e.printStackTrace();
}
}
#Override
public void paintComponent(Graphics g)
{
// Draw the previously loaded image to Component
g.drawImage(img, 0, 0, null);
super.paintComponent(g);
}
}
I am trying to use Painter to make a certain jpg become my background.
mapScreen = new Form("Map");
try
{
Image image = Image.createImage("/res/try.jpg");
map = new Map(image);
mapScreen.addComponent(map);
} catch (Exception e)
{
System.out.print("Error\n\n"+e.getMessage());
mapScreen.addComponent(new Label(e.getMessage()));
}
And for the map class,
public Map(Image image)
{
this.mapImage = image;
painter = new Painter()
{
public void paint(Graphics g, Rectangle clippingRect)
{
g.clipRect(0, 0, getWidth(), getHeight());
g.drawImage(mapImage, getX(), getY());
}
};
}
public void initComponent()
{
setX(0);
setY(0);
getSelectedStyle().setBgTransparency(0);
getSelectedStyle().setBgPainter(painter);
getUnselectedStyle().setBgTransparency(0);
getUnselectedStyle().setBgPainter(painter);
}
The problem with this is that the image doesn't show up at all and when I try to debug, It doesn't even enter the paint(Graphics g, Rectangle clippingRect)...
The code
try
{
Image image = Image.createImage("/res/try.jpg");
map = new Map(image);
mapScreen.addComponent(map);
}
is successful.
Can anyone tell me how to do it properly?
And also, if anyone know how to do panning on an image larger than the size of the screen, Can you help me with that also? Thanks.
Use setBgTransparency to 255 and don't call the clipRect method.
You can look at the bg painter code within Component.java which is pretty flexible.
I am a java beginner and for my first project I started building a Monopoly game.
I'm building the GUI in SWING using the Graphics method.
Two problems appeared which I can't find an answer to.
The first one is that it seems that I can't set the Background color to my JPanel which I had previously done the same way in another JPanel in the same project.
The second one is that I get a NullPointerException while trying to add an image.I managed to correct this error with a try/catch but it seems that the Graphics won't paint.Again I've used the same method to load and add images in a previous JPanel and it worked.
I should mention that my JFrame at the moment contains 3 elements everyone in there separate classes and are added via BorderLayout().
This is the code for the class that is creating problems:
public class MonopolyBoard extends JPanel{
Image atlantic;
MonopolyBoard() {
this.setBorder(new EtchedBorder());
this.setBackground(new Color( (80), (180), (210) )); //this code dosent work
//this throws exception without try catch
try{
ImageIcon a = new ImageIcon(this.getClass().getResource("../Card/Atlantic Ave.jpg"));
atlantic = a.getImage();
}
catch(NullPointerException e){}
}
public void paint(Graphics g){
}
Graphics2D g2 = (Graphics2D) g;
//this code should draw the image but it dosent
g2.drawImage(atlantic, 100, 100, null);
g.drawImage(atlantic, 100, 100, this);
};
}
You won't know unless you print the stacktrace inside the catch block. If the constructor, new ImageIcon(), isn't throwing the exception and instead is returning a null object, the next line, a.getImage(), will definitely cause a NPE because you can't call a method on a null object.
Instead of this
//this throws exception without try catch
try
{
ImageIcon a = new ImageIcon(this.getClass().getResource("../Card/AtlanticAve.jpg"));
atlantic = a.getImage();
}
catch(NullPointerException e){}
Try this
// the next line may be wrapped incorrectly due to MarkDown
ImageIcon a = new ImageIcon(this.getClass().getResource("../Card/AtlanticAve.jpg"));
if (a == null)
{
System.out.println("Can not find AtlanticAve.jpg");
return;
}
atlantic = a.getImage();
The line
// the next line may be wrapped incorrectly due to MarkDown
ImageIcon a = new ImageIcon(this.getClass().getResource("../Card/AtlanticAve.jpg"));
Basically, you need to start by seeing what might cause the constructor if ImageIcon to return a null object. That will get you on the right track. It might be something due to a failed getResource() call. A simple way of finding out would be to separate the above line into it's parts and give them their own result variables. It's messy and ineficient but that's how troubleshooting goes sometimes.
// using _var_ because I'm too lazy to look up the return types of the methods
var x1 = this.getClass().getResource("../Card/AtlanticAve.jpg");
if (x1 == null)
{
System.out.println("Can't find my resource");
}
You get the picture
I am very confused with your code but I think the problem is that your panel is not drawing!, your paint method it should be
#Override
public void paintComponent(Graphics g){
Graphics2D g2 = (Graphics2D) g;
//this code should draw the image but it dosent
g2.drawImage(atlantic, 100, 100, null);
g.drawImage(atlantic, 100, 100, this);
}
Setting the Background color does not have any effect because you override paint().
Paint is responsible for drawing the background.
You need to paint the background in your paint method:
public void paint(Graphics g){
// paint the background
g.fill(); // not sure about the parameters
// paint your image
g.drawImage(...);
}
Read edit 2 for what I'm actually missing to make it work
I'm currently trying to create some custom JButtons using images created in photoshop that have an alpha parameter.
So far, overriding the paint() method to draw the image has worked in the sense that the button is drawn showing the correct image. I'd like to improve it, though, by making its shape (clickable area) the same as the visible pixels on the image (right now if I draw the button's border, it's a square).
Is there an easy way to do that or do I have to parse the image and find the alpha pixels to make a custom border?
Which methods would I have to override to make it work the way I want?
Also, another question I'm going to have later: would it be better to use some kind of algorithm to change the images' colors to make it seem like it is being clicked when people click on it or am I better off creating a second image and drawing that one while the button is active?
Edit: I just read on some other question that I should redefine paintComponent() instead of paint(), I'd like to know why since redefining paint() works fine?
Edit 2: I changed everything to make sure my JButtons are created using the default constructor with an icon. What I'm trying to do is get the X and Y position of where the click was registered and grab the icon's pixel at that position and check its alpha channel to see if it is 0 (if it is, do nothing, else do the action it is supposed to do).
The thing is, the alpha channel always returns 255 (and blue, red and green are at 238 on transparent pixels). On other pixels, everything returns the value it should be returning.
Here's an example (try it with another image if you want) that recreates my problem:
public class TestAlphaPixels extends JFrame
{
private final File FILECLOSEBUTTON = new File("img\\boutonrondX.png"); //My round button with transparent corners
private JButton closeButton = new JButton(); //Creating it empty to be able to place it and resize the image after the button size is known
public TestAlphaPixels() throws IOException
{
setLayout(null);
setSize(150, 150);
closeButton.setSize(100, 100);
closeButton.setContentAreaFilled(false);
closeButton.setBorderPainted(false);
add(closeButton);
closeButton.addMouseListener(new MouseListener()
{
public void mouseClicked(MouseEvent e)
{
}
public void mousePressed(MouseEvent e)
{
}
public void mouseReleased(MouseEvent e)
{
System.out.println("Alpha value of pixel (" + e.getX() + ", " + e.getY() + ") is: " + clickAlphaValue(closeButton.getIcon(), e.getX(), e.getY()));
}
public void mouseEntered(MouseEvent e)
{
}
public void mouseExited(MouseEvent e)
{
}
});
Image imgCloseButton = ImageIO.read(FILECLOSEBUTTON);
//Resize the image to fit the button
Image newImg = imgCloseButton.getScaledInstance((int)closeButton.getSize().getWidth(), (int)closeButton.getSize().getHeight(), java.awt.Image.SCALE_SMOOTH);
closeButton.setIcon(new ImageIcon(newImg));
}
private int clickAlphaValue(Icon icon, int posX, int posY)
{
int width = icon.getIconWidth();
int height = icon.getIconHeight();
BufferedImage tempImage = (BufferedImage)createImage(width, height);
Graphics2D g = tempImage.createGraphics();
icon.paintIcon(null, g, 0, 0);
g.dispose();
int alpha = (tempImage.getRGB(posX, posY) >> 24) & 0x000000FF;
return alpha;
}
public static void main(String[] args)
{
try
{
TestAlphaPixels testAlphaPixels = new TestAlphaPixels();
testAlphaPixels.setVisible(true);
testAlphaPixels.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
catch(IOException ioe)
{
ioe.printStackTrace();
}
}
}
This is just a wild guess, but is it possible that when my image gets cast to an Icon, it loses its Alpha property and thus doesn't return the correct value? Anyway, I'd really appreciate it if someone could actually help me out and tell me what I should be changing to get the correct value.
I'm guessing that because when I try it with the original image, the alpha channel's value is fine, but I can't actually use that BufferedImage because I resize it, so I actually get the channel values of the image with the original size...
I think you are on the wrong way. You do not have to override neither paint() nor paintComponent() methods. JButton already "knows" to be shown with image only:
ImageIcon cup = new ImageIcon("images/cup.gif");
JButton button2 = new JButton(cup);
See the following tutorial for example: http://www.apl.jhu.edu/~hall/java/Swing-Tutorial/Swing-Tutorial-JButton.html
Moreover swing is fully customized. You can control opacity, border, color etc. You probably should override some mentioned methods to change functionality. But in most cases there is better and simpler solution.
Since there were good elements in multiple answers, but none of the answers were complete on their own, I'll answer my own question so other people that have the same problem can try something similar.
I created my buttons using a new class which extends JButton, with a new constructor that takes a BufferedImage as parameter instead of an icon. The reason for that is that when I did something like myButton.getIcon(), it would return an Icon, then I'd have to make various manipulations on it to make it a BufferedImage of the right size, and it ended up not working anyway because it seems like the first cast to Icon made it lose the alpha data in the pixels, so I couldn't check to see if the user was clicking on transparent pixels or not.
So I did something like this for the constructor:
public class MyButton extends JButton
{
private BufferedImage bufImg;
public MyButton(BufferedImage bufImg)
{
super(new ImageIcon(bufImg));
this.bufImg = bufImg;
}
}
Then I created an accessor for my bufImg that resized the image to fit the JButton using the getSize() method and then returned an image resized at the right size. I do the transformations in the getBufImg() accessor because the image size might change when the window gets resized. When you call the getBufImg(), it's usually because you clicked on the button and thus you're not currently resizing the window.
Something a little bit like this will return the image at the right size:
public BufferedImage getBufImg()
{
BufferedImage newImg = new BufferedImage(getSize().getWidth(), getSize().getHeight(), BufferedImage.TYPE_INT_ARGB); //Create a new buffered image the right size
Graphics2D g2d = newImg.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.drawImage(bufImg, 0, 0, getSize().getWidth(), getSize().getHeight(), null);
g2d.dispose();
return newImg;
}
With that buffered image, you can then code a method like this:
private int clickAlphaValue(BufferedImage bufImg, int posX, int posY)
{
int alpha;
alpha = (bufImg.getRGB(posX, posY) >>24) & 0x000000FF; //Gets the bit that contains alpha information
return alpha;
}
That you call on the button that implements a MouseListener, like this:
myButton.addMouseListener(new MouseListener()
{
public void mouseClicked(MouseEvent e)
{
}
public void mousePressed(MouseEvent e)
{
}
public void mouseReleased(MouseEvent e)
{
if(clickAlphaValue(((myButton)e.getSource()).getBufImg(), e.getX(), e.getY()) != 0) //If alpha is not set to 0
System.exit(0); //Or other things you want your button to do
}
public void mouseEntered(MouseEvent e)
{
}
public void mouseExited(MouseEvent e)
{
}
});
And voila! The button will only do the action if you clicked on non-transparent pixels.
Thanks for the help everyone, I couldn't have come up with this solutions on my own.
If you want to have shape-specific click points, you're better off using Shape and their contains method. If you want, you can create a shape when creating your custom button class as part of it, and implement a contains method by wrapping around the shape's contains method.
As for the custom JButton, create a class that extends JButton, like this:
import java.awt.*;
import javax.swing.*;
public class CustomButton extends JButton{
/** Filename of the image to be used as the button's icon. */
private String fileName;
/** The width of the button */
private int width;
/** The height of the button. */
private int height;
public CustomButton(String fileName, int width, int height){
this.fileName = fileName;
this.width = width;
this.height = height;
createButton();
}
/**
* Creates the button according to the fields set by the constructor.
*/
private void createButton(){
this.setIcon(getImageIcon(filename));
this.setPreferredSize(new Dimension(width, height));
this.setMaximumSize(new Dimension(width, height));
this.setFocusPainted(false);
this.setRolloverEnabled(false);
this.setOpaque(false);
this.setContentAreaFilled(false);
this.setBorderPainted(false);
this.setBorder(BorderFactory.createEmptyBorder(0,0,0,0));
}
}
Here's how you can load the ImageIcon, if you want to do it like this.
public ImageIcon getImageIcon(String fileName){
String imageDirectory = "images/"; //relative to classpath
URL imgURL = getClass().getResource(imageDirectory + fileName);
return new ImageIcon(imgURL);
}
This will give you a button that will at least look like your image.
I asked a similar question regarding Image-based events on click, and Shapes helped wonders.
I guess it comes down to how complex your button images are.
Here's reference anyway:
How can you detect a mouse-click event on an Image object in Java?
PS: Maybe look into generating shapes from images, that go around all the pixels that aren't transparent. No idea if this is possible, but it would mean that a button would only be "pressed" if the user clicks on the image part of it. Just a thought.
If you want your button layout to be that of the non-transparent pixels in your image, then you should redefine the paintComponent() method. It is the most correct way of doing it (overriding paint() worked in old times but is now discouraged).
However I think it is not exactly what you want: you want a click on the button to be detected only if it is on a non-transparent pixel, right? In that case you have to parse your image and when clicked compare mouse coordinates to the pixel alpha channel of your image as JButton does not have such a feature.
If you have a round button, this is exactly what you need:
public class RoundButton extends JButton {
public RoundButton() {
this(null, null);
}
public RoundButton(Icon icon) {
this(null, icon);
}
public RoundButton(String text) {
this(text, null);
}
public RoundButton(Action a) {
this();
setAction(a);
}
public RoundButton(String text, Icon icon) {
setModel(new DefaultButtonModel());
init(text, icon);
if(icon==null) return;
setBorder(BorderFactory.createEmptyBorder(0,0,0,0));
setContentAreaFilled(false);
setFocusPainted(false);
initShape();
}
protected Shape shape, base;
protected void initShape() {
if(!getBounds().equals(base)) {
Dimension s = getPreferredSize();
base = getBounds();
shape = new Ellipse2D.Float(0, 0, s.width, s.height);
}
}
#Override public Dimension getPreferredSize() {
Icon icon = getIcon();
Insets i = getInsets();
int iw = Math.max(icon.getIconWidth(), icon.getIconHeight());
return new Dimension(iw+i.right+i.left, iw+i.top+i.bottom);
}
#Override public boolean contains(int x, int y) {
initShape();
return shape.contains(x, y);
//or return super.contains(x, y) && ((image.getRGB(x, y) >> 24) & 0xff) > 0;
}
}
JButton has a contains() method. Override it and call it on mouseReleased();
paintComponent() instead of paint() depends if you paint() inside XxxButtonUI or just override paintComponent(), but there exists the option JButton#setIcon.