1. Steganography in halftone images: conjugate error diffusion
Source: Signal processing, Vol. 83, 2003, pp
Authors: M.S. Fu and C. Au
Speaker: J. C. Chuang

2. Stacking

3. Visual cryptography Steganography review
Binary O1 + Binary O2-> Binary O3
Noar & Shamir, (2, 2), secret (binary image), 1994
Hwang & Chang, (3, 3), secret (binary image), 2001
Gray O1 + Gray O2-> Gray O3 (Current, halftone technique)
Lin & Tsai, secret (binary image), 2003
Pei & Guo, secret (binary image), 2003
Color O1 + Color O2-> Color O3 (CMYK)
Hou, secret (halftone color image), 2003

4. Error Diffusion 1 2 <T (128) Two kernels Steinberg kernel
Jarvis kernel

5. 3 4 依此類推 Error=-105 130+(7/16)*(-105)=93 100+(1/16)*(-105)=93
150+(5/16)*(-105)=117
Error=93-0=93
120+(7/16)*(93)=161 4
100+(1/16)*(93)=106
93+ (5/16)*(93)=122
Error= =94
117+(3/16)*(93)=134
依此類推

6. Data hiding by conjugate error diffusion (DHCED)
國立中正大學
Share 1
Share 2
Watermark

7. Share 1 (Halftone, binary)
Error diffusion
Share 1 (gray-level)
Share 1 (Halftone, binary)
F(.)
Error diffusion
Share 2 (gray-level)
Share 2 (Halftone, binary)

8. Share 2 (ideal case)
Watermark, (1, 白) (0, 黑)
Share-1, (1, 白) (0, 黑)

9. 93<T=127, 黑色(0)
△=128-93=35
T2=20

10. Conclusion
Secret (Gray-level image)
Color image (RGB)