  This paper presents techniques for digital image watermarking based on
eigenvalue decomposition of normal matrices. The introduced methods are
convenient and self-explanatory, achieve satisfactory results, as well as
require less and easy computations compared to some current methods. Through
the proposed methods, host images and watermarks are transformed to the space
of normal matrices, and the properties of spectral decompositions are dealt
with to obtain watermarked images. Watermark extraction is carried out via a
procedure similar to embedding. Experimental results are provided to illustrate
the reliability and robustness of the methods.
