How to convert pixel data to grayscale image in java?

I 've gray pixels but don't kn开发者_StackOverflow中文版ow to create gray scale image

Create grayscale image on the fly in Java (from http://technojeeves.com/joomla/index.php/free/89-create-grayscale-image-on-the-fly-in-java)

import java.awt.*;
import java.awt.color.*;
import java.awt.image.*;

import java.io.*;

import javax.imageio.ImageIO;


public class BMP {
/**
 * (Testing only)
 */
public static void main(String[] args) throws Exception {
    BMP.makeMeCross(args[0]);
}

/**
 *
 * @param filename The file name for the 'crosshair' image
 *
 * @throws IOException If the file could not be written to by ImageIO
 */
public static void makeMeCross(String filename) throws IOException {
    int sz = 101;
    byte[] buffer = new byte[sz * sz];

    for (int i = 0; i < sz; i++) {
        for (int j = 0; j < sz; j++) {
            // Make a 'crosshair' pattern
            buffer[(i * sz) + j] = ((j == 50) || (i == 50)) ? (byte) 255 : 0;
        }
    }

    ImageIO.write(BMP.getGrayscale(101, buffer), "PNG", new File(filename));
}

/**
 *
 * @param width The image width (height derived from buffer length)
 * @param buffer The buffer containing raw grayscale pixel data
 *
 * @return THe grayscale image
 */
public static BufferedImage getGrayscale(int width, byte[] buffer) {
    int height = buffer.length / width;
    ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
    int[] nBits = { 8 };
    ColorModel cm = new ComponentColorModel(cs, nBits, false, true,
            Transparency.OPAQUE, DataBuffer.TYPE_BYTE);
    SampleModel sm = cm.createCompatibleSampleModel(width, height);
    DataBufferByte db = new DataBufferByte(buffer, width * height);
    WritableRaster raster = Raster.createWritableRaster(sm, db, null);
    BufferedImage result = new BufferedImage(cm, raster, false, null);

    return result;
}
}

There is a javax.swing.GrayFilter worth to look at for this purpose. It can be used like this:

Icon icon = myLabel.getIcon();
Image img = gc.createCompatibleImage(icon.getIconWidth(), icon.getIconHeight(), Transparency.TRANSLUCENT);
icon.paintIcon(this, img.getGraphics(), 0, 0);
img = GrayFilter.createDisabledImage(img);
myLabel.setIcon(new ImageIcon(img));