I am trying to draw a portion of a circular game board. This board rotates, but I'd like to keep a constant viewport. My plan was to create a BufferedImage of the full board, rotate it, then draw a centered portion with a graphics paint method. However, Graphics does not have a rotate, and Graphics2D does not have a way to draw a portion of the image.
Any thoughts?
"Graphics2D does not have a way to draw a portion of the image."
That's not true. Graphics2D inherits from Graphics this method. Which allows drawing portions of an image. see an example usage here
public abstract boolean drawImage(Image img,
int dx1,
int dy1,
int dx2,
int dy2,
int sx1,
int sy1,
int sx2,
int sy2,
ImageObserver observer)
Draws as much of the specified area of the specified image as is currently available, scaling it on the fly to fit inside the specified area of the destination drawable surface. Transparent pixels do not affect whatever pixels are already there.
Parameters:
- img - the specified image to be drawn. This method does nothing if img is null.
- dx1 - the x coordinate of the first corner of the destination rectangle.
- dy1 - the y coordinate of the first corner of the destination rectangle.
- dx2 - the x coordinate of the second corner of the destination rectangle.
- dy2 - the y coordinate of the second corner of the destination rectangle.
- sx1 - the x coordinate of the first corner of the source rectangle.
- sy1 - the y coordinate of the first corner of the source rectangle.
- sx2 - the x coordinate of the second corner of the source rectangle.
- sy2 - the y coordinate of the second corner of the source rectangle.
- observer - object to be notified as more of the image is scaled and converted.
You can cast to Graphics 2D
How to rotate Graphics in Java
in order to get it rotatin'.
To draw a portion of it, I think you can use the clip method
http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics2D.html#clip(java.awt.Shape)
and give it an appropriate shape.
As mentioned by others:
Graphics2D extends Graphics and inherits all the methods of the parent class.Graphics object passed to Swing components should be a Graphics2D instance.In this code, I side step the 2nd assumption by painting to a BufferedImage displayed in a JLabel. In the top of the GUI we can see the 'complete' image obtained from Example images for code and mark-up Q&As. In the bottom the code crops the image to just the 'black' king, rotates it and paints a clipped version (repeatedly).
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import java.net.URL;
import java.util.Random;
import javax.imageio.ImageIO;
class ClippedRotatedImage {
public static void main(String[] args) throws Exception {
URL url = new URL("https://i.stack.imgur.com/memI0.png");
final BufferedImage bi = ImageIO.read(url);
Runnable r = new Runnable() {
@Override
public void run() {
JPanel gui = new JPanel(new BorderLayout());
gui.add(new JLabel(
new ImageIcon(bi)),
BorderLayout.PAGE_START);
final BufferedImage bi2 = new BufferedImage(
400,
150,
BufferedImage.TYPE_INT_RGB);
final JLabel l = new JLabel(
new ImageIcon(bi2), SwingConstants.CENTER);
gui.add(l, BorderLayout.CENTER);
ActionListener animatonListener = new ActionListener() {
Random rnd = new Random();
@Override
public void actionPerformed(ActionEvent e) {
Graphics2D g = bi2.createGraphics();
int x = rnd.nextInt(bi2.getWidth());
int y = rnd.nextInt(bi2.getHeight());
double theta = rnd.nextDouble()*2*Math.PI;
g.rotate(theta);
g.setClip(x,y,64,64);
g.drawImage(bi,x,y,null);
g.dispose();
l.repaint();
}
};
Timer timer = new Timer(50, animatonListener);
timer.start();
JOptionPane.showMessageDialog(null, gui);
timer.stop();
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency
SwingUtilities.invokeLater(r);
}
}
