how to detect circles in an image code example

Example 1: detect a circle in an image along with radius and color

[centers,radii] = imfindcircles(rgb,[20 25],'ObjectPolarity','dark', ...
          'Sensitivity',0.95);

delete(h)
viscircles(centers,radii);

Example 2: detect a circle in an image along with radius and color

[centers,radii] = imfindcircles(rgb,[20 25],'ObjectPolarity','dark', ...
    'Sensitivity',0.9)

Example 3: detect a circle in an image along with radius and color

h = viscircles(centers,radii);