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Methods and Apparatus for Hiding Data in Halftone Images

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.
Technology Benefits
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
Technology Application
- Embedding information
Supplementary Information
Patent Number: US7804977B2
Application Number: US2006508410A
Inventor: Au, Oscar Chi-Lim | Fu, Ming Sun
Priority Date: 14 Aug 2000
Priority Number: US7804977B2
Application Date: 22 Aug 2006
Publication Date: 28 Sep 2010
IPC Current: G06K000900
US Class: 382100 | 382156 | 382274 | 382276
Assignee Applicant: The Hong Kong University of Science & Technology
Title: Methods and apparatus for hiding data in halftone images
Usefulness: Methods and apparatus for hiding data in halftone images
Summary: For transforming gray-scale image into halftone image during transmission of document containing computer-generated logos through facsimile.
Novelty: Converting method for transforming gray-scale image into halftone image involves performing error diffusion on gray-scale image based on determined error values to convert multiple gray-scale image pixels to halftone image pixels
Sub Category
Computer System
Application Date
22 Aug 2006
Application No.
US 11/508410
Patent Information
US 7804977
ID No.
Hong Kong

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