BufferedImage Help

Question

I posted a question in sun java forums sometime ago and i am finding it hard to understand the first response i received from the replier though it seems he gave me the correct approach to my problem. The link to the question is:

http://forums.sun.com/thread.jspa?threadID=5436562&tstart=0

Someone replied that i should use BufferedImage and make tiles. I don't really understand what the tiles mean in connection with the BufferedImage.

I would like someone to explain to me what the tiles are and how they are created in the BufferedImage.

I have searched the web for a while but couldn't find any link that can help me understanding the basics of the tiles and creating the tiles. Any pointer to a site is also appreciated.

I need help in understanding the tiles in connection with the BufferedImage and also how they are created.

Answer 1

A "tile" in a 2D game simply means an "image smaller than whole screen that you can reuse several times to create the background".

Here's a a working example where four tiles are created (adding some random noise to every pixel). Each tile is 50x50 pixels.

Then there's a "map" (that you call a "grid" in your case) representing which tiles you want to put where.

From that map, a bigger BufferedImage is created (note that it's just an example, in a real program you'll want to use a BufferedImage copy, not a pixel-by-pixel copy).

The map is 9x7, each tile is 50x50 pixels, hence the resulting image is 9*50 x 7*50 (ie 450 by 350).

Note that the following is really just a simple example, as short as possible, showing how to create a bigger BufferedImage using several tiles: the goal is not to give a tutorial on best Swing usage nor on how to squeeze every bit of performances out of BufferedImages, etc.

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;

public class ToyTiled extends JFrame {

    private static final int IMAGE_TYPE = BufferedImage.TYPE_INT_ARGB;

    private BufferedImage img;

    public static void main( String[] args ) {
        new ToyTiled();
    }

    public ToyTiled() {
        super();
        this.add(new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                g.drawImage(img, 0, 0, null);
            }

        });
        img = new BufferedImage( 450, 350, IMAGE_TYPE );   // here you should create a compatible BufferedImage
        this.setSize(img.getWidth(), img.getHeight());
        this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);


        final int NB_TILES = 4;
        BufferedImage[] tiles = new BufferedImage[NB_TILES];
        tiles[0] = createOneTile( new Color( 255, 255, 255 ) );
        tiles[1] = createOneTile( new Color( 255,   0, 255 ) );
        tiles[2] = createOneTile( new Color(   0,   0, 255 ) );
        tiles[3] = createOneTile( new Color(   0, 255, 255 ) );  

        final int[][] map = new int[][] {
                { 1, 0, 2, 3, 0, 1, 2, 2, 2 },
                { 0, 2, 3, 0, 1, 2, 2, 2, 3 },
                { 1, 0, 2, 3, 0, 1, 2, 2, 2 },
                { 2, 1, 0, 1, 2, 3, 2, 0, 0 },
                { 1, 0, 2, 3, 0, 1, 2, 2, 3 },
                { 1, 0, 2, 2, 1, 1, 2, 2, 3 },
                { 1, 0, 2, 3, 0, 1, 2, 2, 3 },
        };

        for (int i = 0; i < map[0].length; i++) {
            for (int j = 0; j < map.length; j++) {
                final BufferedImage tile = tiles[map[j][i]];
                for (int x = 0; x < tile.getWidth(); x++) {
                    for (int y = 0; y < tile.getHeight(); y++) {
                        img.setRGB( x + i * 50, y + j * 50, tile.getRGB(x,y) );
                    }
                }
            }
        }

        this.setVisible( true );
    }

    private BufferedImage createOneTile( final Color c ) {
        final Random r = new Random();
        final BufferedImage res = new BufferedImage( 50, 50, IMAGE_TYPE );
        for (int x = 0; x < res.getWidth(); x++) {
            for (int y = 0; y < res.getHeight(); y++) {
                res.setRGB( x, y, c.getRGB() - r.nextInt(150) );
            }
        }
        return res;
    }

}

Answer 2

If you want to rotate a portion of a BufferedImage you might find these classes/methods useful:

• AffineTransform.getRotateInstance or AffineTransform.getQuadrantRotateInstance
• AffineTransformOp
• BufferedImage.getSubImage()
• BufferedImage.setData

Example:

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.awt.image.BufferedImageOp;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.WindowConstants;

public class TileTest extends JFrame {

    public static void main(String[] args) throws IOException {
        URL logo = new URL("http://sstatic.net/so/img/logo.png");
        TileTest tileTest = new TileTest(ImageIO.read(logo));
        tileTest.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        tileTest.setVisible(true);
    }

    private TileTest(BufferedImage image) throws IOException {
        this.image = image; 
        setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));
        JLabel label = new JLabel(new ImageIcon(image));
        add(label);
        BufferedImage tile = image.getSubimage(0, 0, 61, 61);
        add(new JButton(new RotateAction(tile, label)));
        pack();
    }

    private BufferedImage image;

}

class RotateAction extends AbstractAction {

    public void actionPerformed(ActionEvent e) {
        BufferedImage tmpImage = op.filter(image, null);
        image.setData(tmpImage.getRaster());
        component.repaint();
    }

    RotateAction(BufferedImage image, Component component) {
        super("Rotate");
        this.component = component;
        this.image = image;
        double x = 0.5 * image.getWidth();
        double y = 0.5 * image.getHeight();
        AffineTransform xfrm =
            AffineTransform.getQuadrantRotateInstance(1, x, y);
        op = new AffineTransformOp(
            xfrm, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
    }

    private final Component component;

    private final BufferedImage image;

    private final BufferedImageOp op;

}