The present invention relates to steganographically hiding images and information.
In a preferred embodiment, an image is hidden within a media signal. The media
preferably includes a cyan (C) color plane, a magenta (M) color plane, a yellow
(Y) color plane and a black (K) color plane. In an alternative embodiment, the
media includes a spot color. The image is converted into a black color channel
image and is then applied to the media's K channel. The black channel image is
inverted and the inverted image is applied to the media's CMY (or spot) color planes.
The C, M and/or Y channels can be investigated to determine whether the image's
signal level should be modified. In a related embodiment, the media signal is segmented
into a plurality of blocks and the detection level of a first embedded block is
determined to be sufficient before the embedding continues to a second block. In
still another embodiment, visible spectrum detection of our out-of-phase digital
watermark provides a clue as to whether a printing process needs calibration or
is misaligned.
