The present invention relates to a method for embedding a watermark into a black
and white or color digital image [D(x)]. Basically the inventive method comprises
the steps of transforming the digital image using a wavelet transform [WC(y)],
transforming a watermark using discrete cosine transform (DCT), integrating the
wavelet-transformed digital image with the DCT-transformed watermark [DW(x)+WC(y)]
to insert the watermark into the image, and generating the watermarked image using
inverse wavelet transform [D(x)]. For color images, RGB mode is converted
into YIQ mode using a conversion matrix and the wavelet transform is applied to
the Y-, I-, Q-values. This inventive digital watermarking of a color image is found
to be highly robust against lossy compression and other image processing operations,
compared to conventionally known methods which are known to be unsuitable for watermarking
color images.