public Bitmap(String filename) throws AWTException {
        bfName = filename;
        bfType = new byte[2];       
        
        try
        {
            DataInputStream is = new DataInputStream( new BufferedInputStream(new FileInputStream(filename)) );
            extractFileHeader(is);
            extractBitmapHeader(is);
            extractImageData(is);
            is.close();
        }
        catch (IOException ioe )
        {
            throw new AWTException(ioe.toString());
        }
        
    }