Remove noise from the image

I have a image of a coin I wanted to make a circular mask to remove noise [Attached mat]

I tried using imfindcircle but it is not working properly

Answer 1

[Bjorn Gustavsson]

First start by trying standard filtering-methods. Compare what you get with 2-D median-filter (medfilt2), and Lee's sigma-filter (wiener2) and see how they perform. After doing that you can check different more advanced image-filters on the file-exchange, for example: bilateral filters, Nonlinear Diffusion filters, total variation filtering and on and on. But first use the basic tools then understand their use and the noise-characteristics in your image. Check the help and documentation to medfilt2 and wiener2.

HTH

[shubham kumar gupta]

tried wiener2 and medianfilt2 they are not working

[Bjorn Gustavsson]

Yes they do, you might have to take further steps after that. Clearly your image have very peculiar non-uniform illumination that you'll also have to correct for.

[shubham kumar gupta]

Its a tilted coin of 180 radius centers not properly known

I tried this first

r=180x_c=180+17;y_c=180+5;

%generate a coordinate grid

[y,x]=ndgrid(0:401,0:401);

%perform calculation

paper= (x-x_c).^2+(y-y_c).^2 <= r^2;

%show result

figure,imshow(paper); %show masked image

for i=1:401

for j=1:401

if paper(i,j)<1

d(i,j)=paper(i,j)*d(i,j);

end

end

end

figure,mesh(d)

rest i'm trying to remove