  A novel digital watermarking for ownership verification and image
authentication applications using discrete wavelet transform (DWT) is proposed
in this paper. Most previous proposed watermarking algorithms embed sequences
of random numbers as watermarks. Here binary images are taken as watermark for
embedding. In the proposed approach, the host image is converted into the YCbCr
color space and then its Y channel decomposed into wavelet coefficients. The
selected approximation coefficients are quantized and then their four least
significant bits of the quantized coefficients are replaced by the watermark
using LSB insertion technique. At last, the watermarked image is synthesized
from the changed and unchanged DWT coefficients. The experiments show that the
proposed approach provides extra imperceptibility and robustness against
wavelet compression compared to the traditional embedding methods in RGB color
space. Moreover, the proposed approach has no need of the original image to
extract watermarks.
