How to get a uniform circle?

Hi I have the following Image of a circle I want to make its edges uniform can any body help ??

Answer 1

[Youssef Khmou]

hi,

i tired to write a fast code, try it and see :

 I=imread('dcircle.png'); % that image with deformed circle.
X=rgb2gray(I);
N=size(X);
%  finding an approximation of the center
% you take where you want start counting 
xc=100;
n=0; %  number of black pixels vertically descending 
for y=1:N(2)

    if X(xc,y)>0.70;
        n=n+1;
    end
end
% the center is then given by :
r=n/4;
yc=N(2)/2;
Y=zeros(N(1),N(2));

 for x=1:N(1)
    for y=1:N(2)

        rt=sqrt(((x-xc)^2)+((y-yc)^2));
        if rt>=r
            Y(x,y)=1;
        end
    end
end
figure,subplot(1,2,1), imshow(X),title(' initial');
subplot(1,2,2), imshow(Y), title(' adjusted');

[Christine Ak]

Thank U Soo Much ,, it was helpful :D

[Image Analyst]

In the FAQ, the vectorized approach to drawing a circle is shown: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F. You might want to use that, or at least learn how to do it.

Answer 2

[Image Analyst]

Get the area and the Equivalent Circular Diameter of the black spot with regionprops. Then use the FAQ or rectangle() to draw a perfect circle.

binaryImage = grayImage < 128;
measurements = regionprops(binaryImage, 'Centroid', 'EquivDiameter');
centroid = [measurements.Centroid]
diameter = measurements.EquivDiameter
% Draw circle in the overlay.
rectangle('Position',[centroid(1)-diameter/2,centroid(2)-diameter/2,diameter, diameter],...
  'Curvature',[1,1],'LineWIdth', 2, 'EdgeColor', 'r');

Attached is the full blown demo. Let me know of any difficulties.

[Christine Ak]

Thx