how to get a crop a circluar region

i wanted to crop a circular region as shown

please can someone help me....

to get the output (a) i used the below code in link

 http://stackoverflow.com/questions/19992097/how-to-do-circular-crop-using-matlab

I = imread('patricia.jpg');
imageSize = size(I);
ci = [250, 300, 100];     % center and radius of circle ([c_row, c_col, r])
[xx,yy] = ndgrid((1:imageSize(1))-ci(1),(1:imageSize(2))-ci(2));
mask = uint8((xx.^2 + yy.^2)<ci(3)^2);
croppedImage = uint8(zeros(size(I)));
croppedImage(:,:,1) = I(:,:,1).*mask;
croppedImage(:,:,2) = I(:,:,2).*mask;
croppedImage(:,:,3) = I(:,:,3).*mask;
imshow(croppedImage);

but the cropping is not coming correctly.... if i binarize and use regionprops the circle is being distorted... please do help

Answer 1

[Walter Roberson]

If the circle is displaying as an ellipse then you need to give the command

axis image

or do the equivalent (axes DataAspect property)