Enhancing embedding of out-of-phase signals

A method of steganographically hiding a digital watermark in an image, the image comprising a plurality of color channels including a black channel and a first color channel, said method comprising the steps of:

• segmenting the image into a plurality of blocks;
• hiding a first digital watermark component in the black channel of a first of the plurality of blocks;
• hiding the component in the first color channel of the first block, the first channel component being inverted with respect to the black channel component;
• detecting the digital watermark component;
• and
• based on the digital watermark detection, reembedding the first block if the detection is below a predetermined threshold, and embedding a second of the plurality of blocks if the detection is above a predetermined threshold.

A method of monitoring a printing process, the printing process providing a print having at least a first color plane and a second color plane, wherein a digital watermark is steganographically embedded in the print by embedding at least one digital watermark component in the first color plane and, at the same print location, embedding the component in the second plane, the second plane component being inverted with respect to the first plane component, said method comprising the steps of:

• capturing a visible spectrum image of the print to provide corresponding scan data;
• analyzing scan data to detect the digital watermark component;
• and
• signaling at least a printing misalignment when the digital watermark component is detected.