private boolean checkRas() throws IOException {
		byte[] a = new byte[14];
		if (read(a) != a.length) {
			return false;
		}
		final byte[] RAS_MAGIC = {0x6a, (byte)0x95};
		if (!equals(a, 0, RAS_MAGIC, 0, 2)) {
			return false;
		}
		format = FORMAT_RAS;
		width = getIntBigEndian(a, 2);
		height = getIntBigEndian(a, 6);
		bitsPerPixel = getIntBigEndian(a, 10);
		return (width > 0 && height > 0 && bitsPerPixel > 0 && bitsPerPixel <= 24);
	}