filtre noir et blanc

salam ,

je ai realisé le programme de detections de contour d une image blan/noir . lors de l execution un message d ereur dans la partie "public inter filterRGB (int x, int y, int rgb) " s affiche . voici mon programme .

 
public class NegatifImage extends Applet
{
  private Image image,
                negatifImage;
 
  public void init ()
  {     
    // Création d'une image et de son négatif
    image        = getImage (getCodeBase (), "image1.jpg");
    negatifImage = createImage (new FilteredImageSource
                                       (image.getSource (),
                                        new FiltreNegatif ()));
  }
 
  public void paint (Graphics gc)
  {
    if (image != null)
    {
      // Affichage des images
      gc.drawImage (image, 0, 0, this);
      gc.drawImage (negatifImage,
                     image.getWidth (this) + 10, 0, this);
    }
  }
}
 
class FiltreNegatif extends RGBImageFilter
{
  private int [] data ;
 private int width ;
 private int hight ;
 public FiltreNegatif (Image Image) {
          this.width = Image.getWidth ();
          this.height = Image.getHeight ();
          this.data = new int [this.width * this.height];

          try {
             PixelGrabber pg = new PixelGrabber (Image,
                               0,
                               0,
                               this.width,
                               this.height,
                               this.data,
                               0,
                               this.width);
             pg.grabPixels ();
          }
          catch (InterruptedException err) {
                throw new RuntimeException ("Chargement interrompu ...");
          }
          if ((pg.getStatus () & ImageObserver.ABORT) != 0) {
             throw new RuntimeException ("Chargement interrompu ...");
          }
       

  public int filterRGB (int x, int y, int rgb)  {
    if (y==0) {
                   return rgb ;
                   }
                  
     int yprevious = y-1 ; 
     if (yprevious < 0 )
     {
         yprevious = this.width - 1;
         }
 
  int previousRGB =this.data[this.width*x + yprevious] ;
 
  int r1 = (rgb >>16 ) & 0xFF;
  int g1= (rgb >>8 ) & 0xFF;
  int b1= rgb  & 0xFF; 
 
  int r2 = ( previousRGB>>16 ) & 0xFF;
  int g2= ( previousRGB>>8 ) & 0xFF ;
  int b2=  previousRGB & 0xFF;
 
  int r3=r1-r2 ;
  int g3=g1-g2 ;
  int b3=b1-b2 ;
                     
    return   r3 | g3 | b3;
  }
}
}

salam ,

je l ai corrigé ca marche ; il se compile mais l excecution donne frame vide