I want to do convolve operation on an image using java. But the program shows a runtime error like cannot do Convolve operation on the image. I am attaching the code I have done. Please help...

import java.awt.image.*;

public class ImageOperations {

    private BufferedImage image, blurredImage = null;
    private int w, h;
    private int rgb[];
    private int red[], green[], blue[];
    //private int x[],freq[];
    private double prob[];

    public final float [] FILTER_3x3 =
    {
        0.1 , 0.1 , 0.1,
	0.1 , 0.4 , 0.1,
	0.1 , 0.1 , 0.1
    };

    public ImageOperations()
    {
        this( null );
    }

    public ImageOperations( BufferedImage image )
    {
        this.image = image;
    }

    public BufferedImage getImage()
    {
       return image;
    }

    public void setImageDetails()
    {
        w = image.getWidth();
        h = image.getHeight();
    }
    public void getImagePixelData( BufferedImage im )
    {
        rgb = new int[ w * h ];
        red = new int[ w * h ];
        green = new int[ w * h ];
        blue = new int[ w * h ];

        rgb = im.getRGB(0, 0, w, h, rgbs, 0, w);
    }

    public void showImageData()
    {

        for(int i = 0; i < rgb.length; i++)
        {
            int tmp = rgb[i];

            red[i] = (tmp & 0x00ff0000) >> 16;
            green[i] = (tmp & 0x0000ff00) >> 8;
            blue[i] = (tmp & 0x000000ff);

            //System.out.printf ( "Red[%d] = %d, Green[%d] = %d, Blue[%d] = %d \n" , i, red[i], i , green[i], i, blue[i] );
        }

        System.out.println( "Image Width & Height is :: " +w+ " " +h );
    }

    public BufferedImage getBlurredImage()
    {
        ConvolveOp cop = new ConvolveOp( new Kernel( 3, 3, FILTER_3x3), ConvolveOp.EDGE_NO_OP, null) );

        if(getImage() == null)
            System.out.println( "Image is null");
        else
        System.out.println( "Image is not null");

        blurredImage = cop.filter( image, blurredImage);   // I'm a bit confused here

        return blurredImage;
    }
}

hmmmm, I'm not your debuger (sure maybe someone), but at 1st. sight

public final double[][] FILTER_3x3 = {
        {0.1, 0.1, 0.1},
        {0.1, 0.4, 0.1},
        {0.1, 0.1, 0.1}
    };

luck with that

I recommend examples from the book:http://filthyrichclients.org/
download Examples
Chapter 8, Image Processing
go to
CustomImageOp and GraphicsUtilities - very useful methods

public final float[] FILTER_3x3 = {
        0.1f, 0.1f, 0.1f,
        0.1f, 0.4f, 0.1f,
        0.1f, 0.1f, 0.1f
    };

Thank you quuba, it was very much helpful. Actually the problem was the image was not compatible to do a convolve operation on. I had to get the Color Model of the image, and had to create a compatible writable raster. Then I am able to do a convolve operation....

So, the code is....

import java.awt.image.*;

public class ImageOperations {

    private BufferedImage image;
    private int w, h;
    private int rgb[], blurredRGBS[];
    private int red[], green[], blue[];
    //private int x[],freq[];
    //private double prob[];

    public static final float [] BLUR_3x3 =
    {
        0.1f , 0.1f , 0.1f,
	0.1f , 0.2f , 0.1f,
	0.1f , 0.1f , 0.1f
    };

    public ImageOperations()
    {
        this( null );
    }

    public ImageOperations( BufferedImage image )
    {
        this.image = image;
    }

    public BufferedImage getImage()
    {
       return image;
    }

    public void setImageDetails()
    {
        w = image.getWidth();
        h = image.getHeight();
    }
    public void getImagePixelData( BufferedImage im )
    {
        rgb = new int[ w * h ];
        red = new int[ w * h ];
        green = new int[ w * h ];
        blue = new int[ w * h ];

        rgb = im.getRGB(0, 0, w, h, rgb, 0, w);
    }

    public void showImageData()
    {

        for(int i = 0; i < rgb.length; i++)
        {
            int tmp = rgb[i];

            red[i] = (tmp & 0x00ff0000) >> 16;
            green[i] = (tmp & 0x0000ff00) >> 8;
            blue[i] = (tmp & 0x000000ff);

            //System.out.printf ( "Red[%d] = %d, Green[%d] = %d, Blue[%d] = %d \n" , i, red[i], i , green[i], i, blue[i] );
        }

        System.out.println( "Image Width & Height is :: " +w+ " " +h );
    }

    public BufferedImage getBlurredImage()
    {
        
        BufferedImage blurredImage = null;

        ColorModel cm = image.getColorModel();
        
        image = new BufferedImage( cm, cm.createCompatibleWritableRaster( w, h ),
                                   cm.isAlphaPremultiplied(), null );

        ConvolveOp cop = new ConvolveOp( new Kernel( 3, 3, BLUR_3x3), ConvolveOp.EDGE_NO_OP, null );

        if(getImage() == null)
            System.out.println( "Image is null");
        else
        System.out.println( "Image is not null");
        
        blurredImage = cop.filter( image, null );

        System.out.println( "Blurring is done");

        return blurredImage;
    }
}