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;
    }
}