Re: [WM]: coefficient in LL subband after 2-D DWT haar =

["shijun xiang" <xiangshijun@gmail.com>]

transform
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Dear Jian Yi,

        About your question, I have ever implemented the approximate =
testing on image DWT transform. I guess that some errors must
exist in your matlab codes. Generally, after performing  2-D DWT =
transformaton, the LL subband coefficients become larger while the
coefficients in other subbands is small, such as most of them less than =
1. In fact, in LL subband, some coefficients will be larger
than 255, but not all coefficients is larger than 255.

        If possible,  I am willing to check your matlab codes for error =
correction.


--
regards. Shijun Xiang

Email: xiangshijun@gmail.com
Homepage: http://datahiding.anyp.cn


On 10/4/06, =1B$B7z0l=1B(B(Jian Yi) <im943084@mail.cpu.edu.tw> wrote:
>
> Dears adviser
> I have a question about the image coefficient in LL subband after 2-d=20
> DWT transformaton.
> I have a gray image , its bit depth is 256.
> Because I try to implement a DWT transformation in MATLAB, I find the=20
> coefficients in the LL subband are always larger 255.
> I use the 'haar' filter, so I think it's ok.
> But, I always study some paper where their experimetn result, LL band=20
> come  DWT haar transform looks the same as the 1/4 origional image. I=20
> dont know why ? the pixels is larger than 255??
> Just like the attachement.
>
>
> I wonder Why?
>
> Is there some concept I misunderstand?
> Is there some parameter needed to be used in MATLAB ?
>
> Please help me.
>
> Thanks your answers for me.
>
>
> Wishes
>
>
> Jian-Yi
>
>


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