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A multiple-level visual secret-sharing scheme without image size expansion. Source: Information Sciences, Vol. 177, Issue. 21, November 1, 2007, pp. 4696-4710. Authors:Yung-Fu Chen, Yung-Kuan Chan, Ching-Chun Huang, Meng-Hsiun Tsai and Yen-Ping Chu Speaker:Chia-Ming Yeh
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A multiple-level visual secret-sharing scheme without image size expansion Source: Information Sciences, Vol. 177, Issue. 21, November 1, 2007, pp. 4696-4710. Authors:Yung-Fu Chen, Yung-Kuan Chan, Ching-Chun Huang, Meng-Hsiun Tsai and Yen-Ping Chu Speaker:Chia-Ming Yeh Date: 05/28/2008
Outline • Introduction • Proposed scheme • Experiment results • Conclusions
Introduction (2/2) • Image without Image Size Expansion • Pixel by Pixel Ryo Ito’s method ( white pixel) ( black pixel)
Proposed Scheme (1/5) • Image without Image Size Expansion • Block by Block block size s = 4 range l = s/2 ~ s
Proposed Scheme (2/5) • (k , k) MLVSS (Multiple-Level Visual Secret-sharing ) Scheme • block (s pixels) by block (s pixels) • Two types of techniques, histogram width-equalization and histogram depth-equalization Create gray-scale histogram Two types of techniques Encryption l Share Image 1 ( 256 ×256 pixels ) Gray-scale secret image ( 256 × 256 pixels ) Reconstructed image (256 × 256 pixels ) Share Image 2 ( 256 × 256 pixels )
Proposed Scheme (3/5) • Ex : (2,2) MLVSS scheme, 256 pixel × 256 pixel image, s = 4 (2×2 block) Min = 19 Max = 206 Pixels = 65536 Gray-scale histogram Gray-scale secret image average color = 65 Secret block
Proposed Scheme (4/5) • Histogram Width-equalization • [ , ] with , the secret block is arranged into • Ex : Min = 19, Max = 206, s = 4, average color = 65 [ 62.3×l +19 , 62.3(l+ 1 )+19 ] Secret block average color = 65
Proposed Scheme (5/5) • Histogram Depth-equalization • , the secret block is arranged into • Ex : 256 × 256 secret image, c = 65, [21845.3×l, 21845.3(l+ 1 )] , Secret block average color = 65
Experimental Results (1/2) width’s scheme depth’s scheme
Experimental Results (2/2) Ryo Ito’s scheme Yang’s scheme width’s scheme depth’s scheme
Conclusions • Histogram depth-equalization often have better reconstructed secret image quality • Proposed scheme improves the quality of reconstructed secret image without expanding the image size