Re: [WM]: a question about cox's algorithm

[anurag Mishra <anurag_cse2003@yahoo.com>]

What do you mean by variance of cox's algorithm?=20
  =20
  The answer to your question is : It will depend upon the gray level of =
your image. For ex., if the image is represented by 8bpp
(256 color) then according to Cox, the 63 coefficients of every block =
will be sorted in descending order, barring DC coefficient
(0,0), select first few largest coefficients and insert the random =
number according to formula given in paper. The random numbers
will be real numbers with mean 0 and variance 1. After embedding them =
the pixels which were integers initially will be converted to
real. They will be rounded off to its nearest values. This does not =
result in much difference in perceptible quality and SIM or PSNR
values.
  =20
  Good Luck
  =20
  Anurag Mishra

=D1=D6=ED=B5 <yanmiao06@mails.gucas.ac.cn> wrote:
  hi all
I am new in this field. And I am about to impelment a variance of cox's =
algorithm. The image is divided in 8 * 8 block, and dct
transform is applied to each block, then insert watermark into each =
block. My questions is this:
1. Dose each pixel in a 8 * 8 block can only be inserted one bit, which =
means a block can at most inject 64 bits infomation?
2. when trasformed using dct, the values are real numbers, but after =
inject the watermark, I have to round real numbers into
integer, because image gray-level or rgb value is represented by =
integer. Dose this affect my final result?

best regards






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