Methods and Apparatus for Hiding Data in Halftone Images
Patent Information:
1. Filing Country: USA
Application No: 11/508410
Filing Date: 22 August 2006
Patent No: 7804977
Issue Date: 28 September 2010
2. Filing Country: USA
Application No: 12/889220
Filing Date: 23 September 2010
Patent No: 8170274
Issue Date: 01 May 2012
Inventor 1: Prof. Oscar Chi Lim, AU
Inventor 2: Mr. Ming Sun, FU

Halftoning is a method to represent multi-tone images using only two-tone colors. Such methods are used widely in computer printers, newspaper/magazine/book publishing, fax machines, etc. From a distance, halftoned images resemble images with multi-tones. This new invention uses Data Hiding Error Diffusion (DHED) and Data Hiding by Smart Pair Toggling (DHSPAT), to hide a potentially large amount of watermarking data in halftone images with either minor or negligible perceptual degradation. The two methods are used in different situations. One situation is when the original multi-tone image is available and error diffusion method is adopted, i.e. the DHED. Another situation is when both the original multi-tone image and the halftoning method are not known. When only the halftone image is available, the DHSPAT should be adopted. DHED gives very high visual quality and has low complexity. DHSPAT is even simpler in complexity, though with comparatively slightly lower quality, it is still visually sound.
Potential Application   Advantage
- Embedding information   1. Hide data with minimal effect on the visual quality of the printout
2. Can hide a large quantity of data
3. Data hiding and extraction procedures are computationally very simple
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