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From: rukmani on 8 Mar 2005 10:33

hi,

I have a basic doubt regarding the use of the functions like FFT2,DCT2
or DWT2. Are these functions are restricted to be used only for images
which have a smooth variation of colour map?
Because when i tried to use these for a 256*256*3 image size it results
in error . Kindly clear my doubt and do tell me whether the colour
image should be preprocessed before applying FFT2 or DCT2 or DWT2.
waitng for someones help,
regds,
rukmani.

From: Dave Robinson on 8 Mar 2005 12:07
rukmani wrote:
>
>
>
> hi,
>
> I have a basic doubt regarding the use of the functions like
> FFT2,DCT2
> or DWT2. Are these functions are restricted to be used only for
> images
> which have a smooth variation of colour map?
> Because when i tried to use these for a 256*256*3 image size it
> results
> in error . Kindly clear my doubt and do tell me whether the colour
> image should be preprocessed before applying FFT2 or DCT2 or DWT2.
> waitng for someones help,
> regds,
> rukmani.

The RGB planes of a colour image are effectively orthogonal data
planes; the easiest way to deal with them, when working in the
frequency domain is to seperate them into 3 independent monochrome
images, then fft2 them seperately. Do whatever you need in the
frequency domain, and assuming you are coming back to the spatial
domain ifft2 them seperately, then recombine the colour planes to
reform a colour image.

Regards

Dave Robinson
From: rukmani on 8 Mar 2005 12:42
Thank u sir for the timely reply . Is this possible for wavelet domain
also...? or is it only for frequency domain..

regds,
rukmani.

From: Dave Robinson on 9 Mar 2005 05:38
rukmani wrote:
>
>
> Thank u sir for the timely reply . Is this possible for wavelet
> domain
> also...? or is it only for frequency domain..
>
> regds,
> rukmani.
>
The RGB planes are notionally independent, so that splitting them and
applying Wavelet processing will work, again if you need a colour
image as the output from your analysis, the very last step is to
recombine the independently processed colour planes for
display/storage.

Regards

Dave Robinson
From: rukmani on 9 Mar 2005 09:12
thank u sir for the timely reply..
regds,
rukmani.

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