A novel grey-level digital watermarking is proposed.This algorithm performs pre-processing operation on grey-level watermark images by using the decomposing technique of bit plane.Each original image is decomposed into two hierarchical levels in DWT domain.The watermark is embedded by quantifying the wavelet coefficients using visual masking characteristic.The algorithm can extract the watermark without the original image.To enhance the security of the watermarking

a pseudorandom sequence controlled by a secret key is used to modulate the watermark.Experimental results have shown that the proposed algorithm is robust against JEPG compression

adding noise and filtering

while the watermarked images have a good quality.