Grabbing pixels

[Shay Gaghe]

Hi
I�m developing a distributed application with RMI. The client will send an Image�s URL address to server, the server will load this image and grabs its pixels to an array, afterward the server will send the data array to the client, the client will create an image from this data array.
I tried to write piece of code that demonstrate this but it seem I misunderstanding here . I would like to receive a code that allows me to provide this idea .

public class CreatingImage extends JPanel{
  Image img=null;
  public CreatingImage(){
    System.out.println("constructor invoked...");
    img = Toolkit.getDefaultToolkit().getImage("C:/JBuilder4/myWork/RMI/BasicRmi/image/character/miri.jpg");
    importPix(img,25,25,50,50);
  }
  public int[] importPix(Image img,int x,int y,int w,int h){
    int[] pixels = new int[w * h];
  PixelGrabber pg = new PixelGrabber(img, x, y, w, h, pixels, 0, w);
    try{
      pg.grabPixels();
    }catch (InterruptedException e) {
      System.err.println("interrupted waiting for pixels!");
      return null;
    }
    if(pg.getStatus()!=0 && ImageObserver.ABORT!= 0 ) {
        System.err.println("image fetch aborted or errored");
        return null;
    }
    //Toolkit.getDefaultToolkit().createImage(b);
    return pixels;
  }

  public void paintComponent(Graphics g){
    super.paintComponent(g);
    g.drawString("shay",25,25);
    g.drawImage(img,25,25,50,50,this);
  }
}

Thanks
Shay Gaghe
[ January 16, 2002: Message edited by: Shay Gaghe ]

[Nathan Pruett]

Okay... I think I have it doing what you want... three things that I added or changed that helped :

Use a MediaTracker to load the Image... this way you can be sure that the Image is fully loaded before you mess with it.

Use a MemoryImageSource to build the Image from the pixel array.

The second error test in the importPix() method was wrong... I changed it to test the mask in the PixelGrabber's status against the ImageObserver.ABORT code.

Here's the code :

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
 
public class CreatingImage extends JPanel {
 
    Image img = null;
    Image newImg = null;
    int[] pixels;
 
    public CreatingImage() {
        System.out.println( "constructor invoked..." );
        img = Toolkit.getDefaultToolkit().getImage( 
                "C:/JBuilder4/myWork/RMI/BasicRmi/image/character/miri.jpg" );
        MediaTracker mt = new MediaTracker( this );
        mt.addImage( img, 0 );
 
        try {
            mt.waitForID( 0 );
            pixels = importPix( img, 25, 25, 50, 50 );
            newImg = exportPix( pixels, 50, 50 );
        }
        catch( InterruptedException x ) {
            System.err.println( "MediaTracker Image loading interrupted!" );
        }
    }
 
    public int[] importPix( Image img, int x, int y, int w, int h ) {
        int[] pixels = new int[ w * h ];
        PixelGrabber pg = new PixelGrabber( img, x, y, w, h, pixels, 0, w);
        try {
            pg.grabPixels();
        }
        catch ( InterruptedException e ) {
            System.err.println("interrupted waiting for pixels!");
            return null;
        }
 
        if ( ( pg.getStatus() & ImageObserver.ABORT ) != 0 ) {
            System.err.println("image fetch aborted or errored");
            return null;
        }
 
        //Toolkit.getDefaultToolkit().createImage(b);
        return pixels;
    }
 
    public Image exportPix( int[] pixels, int w, int h ) {
        int[] pixelBuffer = new int[ w * h ];
        System.arraycopy( pixels, 0, pixelBuffer, 0, w * h );
        MemoryImageSource memImage = new MemoryImageSource( w, h, pixelBuffer, 0, w );
        return( Toolkit.getDefaultToolkit().createImage( memImage ) );
    }
 
    public void paintComponent( Graphics g ) {
        super.paintComponent(g);
        g.drawString( "shay", 25, 25 );
        g.drawImage( img, 25, 25, 50, 50, this);
        g.drawImage( newImg, 75, 75, this );
    }
 
    public static void main( String[] arg ) {
        JFrame f = new JFrame( "CreatingImage test" );
        CreatingImage ci = new CreatingImage();
        f.getContentPane().add( ci );
        f.addWindowListener( new WindowAdapter() {
            public void windowClosing( WindowEvent e ) {
                System.exit( 0 );
            }
        } );
        f.setSize( 300, 300 );
        f.show();
    }
}

-Nate