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     1 M.Barni, F. Bartolini, V. Cappellini, A. Piva. "A DCT-Domain
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     2 System for Robust Image Watermarking",
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     3 Signal Processing, vol.66, pp 357-372, 1998.
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     4 
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     5 V. Fotopoulos, A.N. Skodras, "A Subband DCT approach to
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     6 image watermarking", X European Signal Processing Conference,
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     7 September 4-8, 2000, Tampere, Finland
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     8 
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     9 parameters:
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    10 for starting coefficient reasonable values for the dct and hartley schemes
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    11 and this kind of dimensions is around 5000-20000, for the watermark length 10000-50000,
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    12 and seed/key should be in the range 1-1000 so that the output file of the testing module
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    13 gives a right similarity diagram
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    14 
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    15 for the subband dct version, things change corresponding to coefficients
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    16 because the bands' sizes are 1/4 of the original image's size.
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    17 starting coef should be between 3000-5000 and length 10000-20000
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    18 for the alpha parameter i use 0.2 for all bands except LL for which i use
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    19 0.1
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    20 
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    21 
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