1. HIDING DATA IN COLOR HALFTONE IMAGES USING DOT DIFFUSION WITH NONLINEAR THRESOLDING
Volume 2, April 2007 April 2007 page(s):Ⅱ-205-Ⅱ-208 Digital Object Identifier /ICASSP
Omid Taheri, Ahmad Movahedian Attar,
ECE Department, Isfahan University of Technology,Isfahan, Iran
Mohammad Mahdi DaneshPanah,
ECE Department, University of Connecticut, Storrs CT, USA
Reporter:趙旻玥
DATE:June

2. OUTLINE 1 Introduction 2 Dot diffusion halftoning method
3 DDNT algorithm for black and white halftone images
4 Generalizing the DDNT algorithm to color halftone images
5 Simulation results
6 Conclusions

3. 1 Introduction To embed hidden data in halftone images
DDNT: dot diffusion with nonlinear thresholding
CDDNT: DDNT’s modification to color halftone images
Main advantage: the hidden pattern’s intesity can be adjusted by three parameters.

4. 2 Dot Diffusion Halftoning Method
For a fixed k:
the halftone pixels:
A class matrix C:M×N
the error:
Neighbors with higher class
numbers are replaced with:
Obtained by parabolic weighting function

5. 3 Dot Diffusion with Nonlinear Thresholding
WDD(i,j) and e(i,j)
X: the original gray-level image
H: the hidden binary image
TDD: the halftoned image obtained by traditional dot diffusion method
WDD: the watermarked halftone image obtained by DDNT algorithm 1 2 3

6. 4 Generalizing DDNT to Color Halfton Images
The dot diffusion must be generalized bo perform on color images: C=[CR CG CB]
The halftone version of C:
The halftoning process:
Three parameters: Mu, Ml, N

7. 5 Simulation Result

8. 6 Conclusions
The intensity of the extracted pattern can be adjusted by three variable parameters in the algorithm.
The visual qualith of the watermarked image is very good and the hidden pattern can be extracted by overlaying the original and watermarked images as well as by a simple XNOR operation.