Obtaining coordinate values within circular ROI

Hello all,

I have a function that receives xlist (vector of row coordinates) and ylist (vector of column coordinates) as inputs. I would like create another function that allows users to just select a starting coordinate (x, y) and it will capture all coordinates within a circular region of radius r (predefined) in the format of xlist and ylist.

My image is always 512*512 (grayscale CT). How do I do this?

Thank you so much!

[Michael Werthmann]

Hello Brian,

I have a similar problem. Die you manage to solve yours?

Regards

Michael

Answer 1

[KSSV]

Check this demo example:

I = imread('cameraman.tif') ;
[ny,nx] = size(I) ;

C = input('Enter center of circle C(x,y), should be less then 256:','s') ;
R = input('Enter Radius of circle:','s') ;
%
C = str2num(C) ;
R = str2num(R) ;

%
th = linspace(0,2*pi) ;
xc = C(1)+R*cos(th) ; 
yc = C(2)+R*sin(th) ; 

[X,Y] = meshgrid(1:nx,1:ny) ;

idx = inpolygon(X(:),Y(:),xc,yc) ;

I(~idx) = 255 ;

imshow(I)

[Michael Werthmann]

Thank You.

I will try that out!