private void writeLSD(OutputStream os, short screen_width, short screen_height, short flags, byte bgcolor, byte aspectRatio) throws IOException	{
		byte[] descriptor = new byte[7]; 
		// Screen_width
	    descriptor[0] = (byte)(screen_width&0xff);
	    descriptor[1] = (byte)((screen_width>>8)&0xff);
	    // Screen_height
	    descriptor[2] = (byte)(screen_height&0xff);
	    descriptor[3] = (byte)((screen_height>>8)&0xff);
		// Global flags
        descriptor[4] = (byte)(flags&0xff);
		// Background color
        descriptor[5] = bgcolor;
		// AspectRatio
	    descriptor[6] = aspectRatio;
	    
	    os.write(descriptor);
	}
Write out a zero length data sub-block
subs/gif-revert/src/main/java/com/engineer/gif/revert/lib/AnimatedGIFWriter.java