How to do circular crop using matlab?

Question

I usually use imcrop to crop rectanguler image but i wat to create circular crop. How to do it?

I know there is another quetion about this, here the link:

1. MATLAB: how do I crop out a circle from an image

   [xx,yy] = ndgrid((1:imageSize(1))-ci(1),(1:imageSize(2))-ci(2));
   mask = (xx.^2 + yy.^2)<ci(3)^2;
   

   and the result of imshow(mask) is rectangle with white background

2. Cropping Circular region of interest around a point in MATLAB

   error in roimaskcc

3. http://www.mathworks.com/matlabcentral/newsreader/view_thread/242489

   [xx,yy]=ndgrid(1:size(X,1), 1:size(X,2));
   CroppingMask= ( (xx-Xcenter).^2+(yy-Ycenter).^2<=Radius^2 );
   X=X.*CroppingMask;
   

   The result of imshow(CroppingMask) is a rectangle with black background with small white circular at the center of the rectangle. When I run line 3 it shows an error.

Please help me, step by step because I'm a beginner.

Here is my image: https://www.dropbox.com/s/5plqzqgyb1ej6gh/patricia.jpg. It resolution is 480x640.

Answer 1

Solution (1) works perfectly well. Here is a complete working example using your image.

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);

It produces the following image.

I hope this clarifies things. There is probably a better way of re-assembling the cropped image, but this was what I could come up with off the top of my head.