Re: [WM]: Question on Barni Paper

[Franco Bartolini <barto@lci.det.unifi.it>]

Dear Gardener,

Question 1.

This is true, it needs to controlthis event. On the other side, the +1 =
offset in the coordinates computation is needed because the
used filters introduce a small delay=20
(misallignement) in the signal (the filter is not
sero phase), that amount to 1 pixel in level 3.

Question 2.

We set 0.2 based on experimental results. Indeed we
changed a few other thongs with respect to [19],
e.g. the term (7) and the (8) itself.

I hope this can help.

Franco Bartolini

gardener wrote:
>=20
> Dear all,
>=20
> I have read the paper of M. Barni, F. Bartolini, and A. Piva, =3D=20
> =3DA1=3DA7Improved wavelet-based watermarking through pixel-wise =3D=20
> masking,=3DA1=3DA8 IEEE Transactions on Image Processing, vol. 10, no =
5,=20
> pp. =3D 783-791, May 2001.
>=20
> =3D20
>=20
> There are some questions for me on page 785, where the authors =3D=20
> introduced and modified the mask construction proposed by Lewis and =
=3D=20
> Knowles. A weighting function w is used to exploit the masking =3D=20
> properties of the HVS. The weighting function is half of the =3D=20
> quantization step, which is the product of three terms, i.e., the =3D=20
> sensitivity of frequency, luminance, and texture. My questions are:
>=20
> =3D20
>=20
> 1.     Indices of Equations of (6) and (8) seem confusing to me. For =
=3D
> example, if the original image with size 512*512 is decomposed into 4=20
> =3D resolution levels (say, level 0 to level 3) through the DWT, then=20
> the =3D size of each level 0 subband is 256*256, i.e., index range =
from=20
> (0,0) to =3D (255, 255), and the size of LL3 subband is 32*32, i.e., =
index range from =3D
> (0,0) to (31, 31). Now, if I want to check the brightness effect of =
=3D pixel (255, 255) on LL0 using equation (6), then index
(32,
> 32) will =3D exceeds LL3 dimensions!?
>=20
> 2.     The power (0.2) of the last term of Equation (3), i.e., a =
measure =3D
> of texture activity, seems different from that (0.034) of Lewis et =3D =

> al=3DA1=3DA6s formula. The authors didn=3DA1=3DA6t explain the reason =
why?
>=20
> Best Regards,
>=20
> =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D
>=20
> gardener
>=20


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