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

[=?big5?B?q9ikQChKaWFuIFlpKQ==?= <im943084@mail.cpu.edu.tw>]

Dears adviser
I have a question about the image coefficient in LL subband after 2-d 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 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 come  DWT haar transform looks the same as the 1/4 origional image. I 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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