BufferedImage's raster

Hi, I have created this simple application:

Code:

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import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.util.Random;

import javax.swing.JFrame;


public class Display extends Canvas implements Runnable{

        /**
        *
        */
        private static final long serialVersionUID = 1L;
        public static final int WIDTH = 1280;
        public static final int HEIGHT = 1024;
        public static final String TITLE = "Title";
       
        private Thread thread;
        private boolean running = false;
        private BufferedImage img;
        private Random rand;
       
        public Display(){
                img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        }
       
        private void start() {
                if(running)
                        return;
                running = true;
                rand = new Random();
                thread = new Thread(this);
                thread.start();
               
        }
       
        @Override
        public void run() {
                while (running){
                        render();
                }
        }
       
       
        public void render(){
                BufferStrategy bs = this.getBufferStrategy();
                if(bs == null){
                        createBufferStrategy(2);
                        return;
                }
               
                Graphics g = bs.getDrawGraphics();
               
                g.drawImage(img, 0, 0, null);
               
                g.drawImage(createImg(WIDTH, HEIGHT), 0, 0, null);
                       
                g.dispose();
                bs.show();
               
        }
       
       
       
        public static void main(String[] args) {
                Display rc = new Display();
                JFrame frame = new JFrame();
                frame.add(rc);
                frame.pack();
                frame.setTitle(TITLE);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setSize(WIDTH, HEIGHT);
                frame.setLocationRelativeTo(null);
                frame.setResizable(false);
                frame.setVisible(true);
               
                rc.start();
        }
       
        public BufferedImage createImg(int width, int height){
               
                BufferedImage imgg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
                int[] pixels = ((DataBufferInt)imgg.getRaster().getDataBuffer()).getData();
               
                for(int i = 0; i < pixels.length;i++){
                        pixels[i] = rand.nextInt();
                }
               
                return imgg;
        }
       
}

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because I wanted to play around with pixels.

I was wondering how does the imgg in createImage() method change without me changing anything in the imgg?
I just fill the pixels array with random numbers and the imgg changes without me actauly doing anything to the imgg.
It would make sense if I would have to do imgg.getRaster().getDataBuffer().setData(pixels);
I have a feeling that it has something to do with the raster.

Quote:

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Originally Posted by PhQ

I was wondering how does the imgg in createImage() method change without me changing anything in the imgg?
I just fill the pixels array with random numbers and the imgg changes without me actauly doing anything to the imgg.
It would make sense if I would have to do imgg.getRaster().getDataBuffer().setData(pixels);
I have a feeling that it has something to do with the raster.

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Let's look at what you're doing:

Code:

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        // create an empty BufferedImage and have imgg refer to it.
        BufferedImage imgg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // extract the data model of the image. This is "live" data -- you change the values held by this array,
        // you will change the image itself.
        int[] pixels = ((DataBufferInt)imgg.getRaster().getDataBuffer()).getData();

        // and that's exactly what you do -- change the values held by the array.
        for(int i = 0; i < pixels.length;i++){
            pixels[i] = rand.nextInt();
        }

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As per the comments, you're changing the raw ints that define the image, not a copy of the data model, but the actual model itself. It should come as no surprise that you'll see your "noise" image when you make these changes.

Quote:

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Originally Posted by Fubarable

Let's look at what you're doing:

Code:

---

        // create an empty BufferedImage and have imgg refer to it.
        BufferedImage imgg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // extract the data model of the image. This is "live" data -- you change the values held by this array,
        // you will change the image itself.
        int[] pixels = ((DataBufferInt)imgg.getRaster().getDataBuffer()).getData();

        // and that's exactly what you do -- change the values held by the array.
        for(int i = 0; i < pixels.length;i++){
            pixels[i] = rand.nextInt();
        }

---

As per the comments, you're changing the raw ints that define the image, not a copy of the data model, but the actual model itself. It should come as no surprise that you'll see your "noise" image when you make these changes.

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Makes sense. Thank you :)

You're welcome!