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From: Eliran Tsarfati on 18 Nov 2009 02:46
Hello,

I'm a student and I get an assignment to add and remove 2D sine noise from a picture.
The picture is "lena.tif";

lena=imread ('lena.tif');
[m,n] = size (lena);

X= repmat ([1:n] / n, [m,1]);
Y= repmat([n,1], [1:m]/m);

I added a sine noise which is: 70sin(5*pi*X+7*pi*Y)

I need to remove the noise in the frequency spatial and the picture spatial.

I know that I need to use fft to remove the noise in the frequency spatial and I also know I need to enter the same sine noise but with opposite phase angle to remove it in the picture spatial.
I don't know how any of those removals, can anyone help with buy explaining me how the algorithms need to work or give a link to a site which explains.
Thanks
From: Rune Allnor on 18 Nov 2009 05:15
On 18 Nov, 08:46, "Eliran Tsarfati" <etzar...(a)hotmail.com> wrote:
> Hello,
>
> I'm a student and I get an assignment to add and remove 2D sine noise from a picture.
> The picture is "lena.tif";
>
> lena=imread ('lena.tif');
> [m,n] = size (lena);
>
> X= repmat ([1:n] / n, [m,1]);
> Y= repmat([n,1], [1:m]/m);
>
> I added a sine noise which is: 70sin(5*pi*X+7*pi*Y)
>
> I need to remove the noise in the frequency spatial and the picture spatial.
>
> I know that I need to use fft to remove the noise in the frequency spatial and I also know I need to enter the same sine noise but with opposite phase angle to remove it in the picture spatial.
> I don't know how any of those removals, can anyone help with buy explaining me how the algorithms need to work or give a link to a site which explains.
> Thanks

This kind of problem is among the most basic in image processing,
and would thus be expected to be mentioned in virtually any
entry-level textbook on image processing. I know the book by
Gonzalez and Woods mentions both why and how it works, and how
to do the filtering.

Rune
From: etzarfat on 18 Nov 2009 06:32
> This kind of problem is among the most basic in image processing,
> and would thus be expected to be mentioned in virtually any
> entry-level textbook on image processing. I know the book by
> Gonzalez and Woods mentions both why and how it works, and how
> to do the filtering.
>
> Rune

Thanks for your help,
I looked in the mentioned book, but they talked about specific filters, I don't want to use the Matlab toolbox, are there other ways?
Thanks
Eliran
From: ImageAnalyst on 18 Nov 2009 06:45
Just follow your professor's instructions, which were take the fft,
locate the spikes, zero out the spikes, and inverse fft. MATLAB has
an fft function so I'm sure you can use that right out of the box.
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