2004 2005 2 2 1G01P095-6
1 6 1.1............................. 6 1.2.............................. 6 2 8 2.1 (Digital Watermark).................... 8 2.1.1........................ 8 2.1.2........................ 9 2.1.3........................ 10 2.1.4........................ 11 2.2......................... 11 2.2.1................... 11 2.2.2........................... 12 2.2.3........................ 12 2.3.............................. 13 3 DCT 14 3.1 DCT( )........................ 14 3.2.................................. 15 3.3......................... 16 3.4.............................. 17 4 18 4.1.................. 18 4.2.............................. 19 5 20 5.1................................. 20 5.2................................... 22 5.3.............................. 23 6 24 6.1.................................. 24 2
6.2............................... 24 3
2.1............................ 9 2.2......................... 10 2.3........................ 10 2.4..................... 13 2.5................... 13 3.1 DCT( )................. 14 3.2......................... 15 3.3......................... 16 4.1.................. 18 4.2 1............. 19 5.1............................. 20 5.2......................... 20 5.3 1................................ 21 5.4 2................................ 22 4
5.1 PSNR......................... 23 5
1 1.1 (Digital Watermark) [1][2] 3 acuagraphy( )[3] [4] DCT( ) DCT 1.2 6 1 6
2 3 DCT DCT 4 5 6 7
2 [5] 2.1 (Digital Watermark) 2.1.1 1. 2. 8
2.1: 2.1.2 1. 2. 1. (invisible digital watermark) 9
2.2: 2.3: 2. (visible digital watermark) 2.1.3 3 10
2.1.4 ID ID 3 ID ( 1 ) 2.2 2.2.1 1 1 1 2 ( ) 8 (0 255) 0 255 11
2.2.2 (pixel) R( ) G( ) B( ) 3 YIQ Y( ) 2 Cb( ) Cr( ) YCbCr RGB 3 1 Y RGB YIQ Y=0.299R+0.587G+0.114B I=0.596R-0.274G-0.322B Q=0.211R-0.523G+0.312B Y R,G,B I,Q YCbCr Y=0.299R+0.587G+0.114B Cb=-0.299R-0.331G-0.500B Cr=0.500R-0.419G+0.081B Y Cb,Cr 2.2.3 2 FFT( 12
) DCT( ) 2.4: 2.5: 2.3 13
3 DCT 2.2.3 DCT( ) DCT JPEG(Joint Photographic Experts Group) JPEG JPEG DCT( ) DCT DCT 3.1 DCT( ) (Discrete Cosine Transform DCT) 3.1: DCT( ) 8 8 P (m, n)m, n = 0, 1,, 7 P (m, n) S(u, v) = 1 7 7 4 C(u)C(v) P (m, n) cos m=0 n=0 (2m + 1)uπ 16 cos (2n + 1)vπ 16 (u, v = 0, 1, 2,, 7) (3.1) 14
DCT C(u), C(v) = 1 2 (u, v = 0) 1 (u, v 0) (3.2) (3.1) P (m, n) = 1 7 7 C(u)C(v)S(u, v) cos 4 m=0 n=0 (2m + 1)uπ 16 cos (2n + 1)vπ 16 (3.3) (3.1) (u, v) 8 8 S(u, v) S(0, 0) (Direct Current DC) 63 S(u, v) (Alternating Current AC) DC AC u v 3.2: 3.2 (3.1) DCT JPEG 3.3 DCT 15
3.3: 3.3 DCT 1 JEPG DCT 16
[5] 8 8 DCT 1 DCT 0 1 DCT 3.3 0 DCT 0 DCT DCT 3.4 DCT ( ) DCT 17
4 3.3 4.1 DCT 0 0 3.3 DCT 0 0 1 DCT 0 1 4.1: ( ) 1 18
1 4.2: 1 4.2 0 19
5 5.1 5.1 256 256 5.2 16 16 2 5.1: 5.2: 3.3 DCT 3.3 20
1 5.1 8 8 32 32 DCT 8 8 16 11 10 16 24 40 51 61 12 12 14 19 26 58 60 55 14 13 16 24 40 57 69 56 14 17 22 29 51 97 80 62 18 22 37 56 68 109 103 77 24 35 55 64 81 104 113 92 49 64 78 87 103 121 120 101 72 92 95 98 112 100 103 99 16 16 32 32 16 16 1 32 32 16 16 5.2 16 16 (3,3) 5.3 5.3: 1 5.2 5.1 21
2 16 16 (6,6) 5.4: 2 1 5.1 5.2 2 ( 5.1) 1 2 5.3 5.4 5.1 PSNR(Peak Signal-to-Noise Ratio) PSNR P SNR = 10 log 10 MAX 2 T, T = 1 M N 22 N 1 i=0 M 1 j=0 ( fij ˆf ij ) 2 (5.1)
(db) MAX N M f ij, ˆf ij (i, j) PSNR PSNR PSNR 40dB (5.1) 5.3 5.4 PSNR 5.1 PSNR JPEG BMP 1 2 PSNR(dB) 37.9 38.5 5.1: PSNR 40dB 2 2 1 40 5.3 5.4 ( 5.1) 5.3 2 23
6 6.1 1 DCT( ) PSNR 6.2 2 PSNR PSNR 24
[1] (ISO/JIS- SCID), 1995 [2] JAPAN COLOR 1997 [3] C4 Technology, http://c4t.jp/index.html [4] AKIHITO38, http://hp.vector.co.jp/authors/va017815/ [5],, 2004 [6],, 2000 [7] JPG2BMP & BMP2JPG, http://www.vector.co.jp/soft/dl/dos/art/se011581.html 25
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