3.1 Encoding a binary pixel p into two shares s1 and s2 60
3.2 Implementing the visual one secret sharing scheme with a pixel expansion of 4 60
3.3 Wu and Chen’s encoding scheme for visual two-secret sharing in two shares 63
3.4 Wu and Chang’s encoding scheme for visual two-secret sharing in two shares 67
3.9 Possible set of encoded patterns for , and sB; and their stacked results for x = 3 84
3.10 Comparison of visual multiple secrets sharing schemes 90
4.1 Comparison of visual cryptography schemes 108
4.2 Approaches to photograph visual cryptography 110
5.1 Values of β for scheme S′ for n = 3. The max over each row is in boldface 146
5.2 Values of β for n = 4. The max over each row is in boldface 146
6.1 Distribution phase of (2, 4)-VCS using Yang et al.’s [25] algorithm 170
6.2 Reconstruction of participant 1 and 2 using Yang et al.’s [25] algorithm 170
6.3 Reconstruction of participant 3 and 4 using Yang et al.’s [25] algorithm 170
6.5 Reconstruction of participant 1 and 2 using Hu and Tzeng [10] algorithm 174
6.6 Reconstruction of participant 1 and 3 using Hu and Tzeng [10] algorithm 174
6.7 Reconstruction of participant 2 and 3 using Hu and Tzeng [10] algorithm 174
7.1 Results of the superimposition of two random pixels 187
7.2 Encoding b into r1 and r2 and results of s = r1 ⊗ r2 by Algorithms 1, 2, and 3. 192
7.3 Light contrasts by Algorithms 1–3 in producing VCRG-2 196
7.5 Light transmissions of the corresponding pixels in Table 7.3. 204
7.6 Light contrasts by Algorithms 4–6 for ( n, n)-VCRG. 206
9.1 Comparison between VCSs with reversing based on perfect black VCSs 276
10.1 Comparisons of different cheating prevention visual secret sharing schemes 295
11.1 The advantages and disadvantages of large and small subpixels 298
11.3 The properties of the misaligned schemes 313
11.4 The relation of the ratios RC,c and R′C, c 317
11.5 The advantages and disadvantages of large and small subpixels 319
15.1 PSNR comparisons for past schemes and our scheme 419
15.3 PSNR comparisons with the Lin-Tsai scheme 421
15.4 PSNR comparisons with the Lin-Tsai scheme 423
16.1 The cover-to-secret image size ratios of the existing schemes and the proposed scheme 458
3.17.75.227