Drawing a Cirlce on an Image using viscircles()

Dear all,

I am trying to put a circle at the center of an image using the folowing code.

clear;clc;
Image   = imread('cameraman.tif');
M       = 128; % cirlce array length 
D       = 0.5; % diameter 
Pupil   = (-fix(M/2):fix((M-1)/2));
figure(1)
imshow(Image)
viscircles([xPupil' xPupil'],D/2.*ones(M,1))

But it looks a pipe from the left corner of the image. I am using 2019a version of Matlab.

I would aprreciate if someone can fix this issue.

Thanks in advance.

Answer 1

[KSSV]

You can draw circle using the below code if center C and radius R of the circle are known.

C = rand(1,2) ;   % center of cricle 
R = 1. ;          % radius of the circle 
m = 100 ;       
th = linspace(0,2*pi,m) ; 
x = C(1)+R*cos(th);
y = C(2)+R*sin(th) ; 
plot(x,y)

[Ash4Matlab]

Hello KSSV,

Thanks for the answer.

Actually I wanted to apply a circular mask on an image and depict that circle (or mask) on the image. For which as far as I know, viscirlces() shouLd work, but I am unable to put the image and the circle togather.

[KSSV]

Why not use the above code, provide center and radius, you can plot circle on the image. To draw a mask, get the indices lying inside the circle using inpolygon and make those indices zero.