how do i create a concentric black and white circles on a color image with different brightness

how do i create a concentric black and white circles on a color image with different brightness from 0 to 255

Answer 1

[Adam Danz]

This uses the gray colormap.

n = 20;      % number of circles
r = [1,10];  % [smallest, largest] radius
center = [0,0]; % center of cirlces (x,y)

radii = linspace(r(1),r(2),n); 
colors = gray(n);   % to reverse colors, colors=flipud(gray(n))
th = linspace(0,2*pi,200);
hold on
for i = 1:n
    x = radii(i) * cos(th) + center(1); 
    y = radii(i) * sin(th) + center(2); 
    plot(x,y,'-','color', colors(i,:), 'LineWidth', 2)
end
axis equal