cannot identify all circles in car tyre

i am trying to separate radial of a car tyre, i have made the following code. it identifies the inside portion of tyre and it cannot detect out the outer portion.

my image

resultant image

my code is

if true
  % code
close all;
clear;
clc;

rgb = imread('C:\Users\Ayush\Desktop\MATLAB SEP 30\images\vertical1.jpg'); figure imshow(rgb) % d = imdistline; gray_image = rgb2gray(rgb);

bw = imbinarize(gray_image); imshow(bw)

% remove all object containing fewer than 30 pixels bw = bwareaopen(bw,30);

% fill a gap in the pen's cap se = strel('disk',2); bw = imclose(bw,se);

% fill any holes, so that regionprops can be used to estimate % the area enclosed by each of the boundaries bw = imfill(bw,'holes');

imshow(bw) [B,L] = bwboundaries(bw,'noholes');

% Display the label matrix and draw each boundary imshow(label2rgb(L, @jet, [.5 .5 .5])) hold on for k = 1:length(B) boundary = B{k}; plot(boundary(:,2), boundary(:,1), 'w', 'LineWidth', 2) end stats = regionprops(L,'Area','Centroid');

threshold = 0.94;

% loop over the boundaries for k = 1:length(B)

% obtain (X,Y) boundary coordinates corresponding to label 'k'
boundary = B{k};

% compute a simple estimate of the object's perimeter
delta_sq = diff(boundary).^2;
perimeter = sum(sqrt(sum(delta_sq,2)));

% obtain the area calculation corresponding to label 'k'
area = stats(k).Area;

% compute the roundness metric
metric = 4*pi*area/perimeter^2;

% display the results
metric_string = sprintf('%2.2f',metric);

% mark objects above the threshold with a black circle
if metric > threshold
  centroid = stats(k).Centroid;
  plot(centroid(1),centroid(2),'ko');
end

text(boundary(1,2)-35,boundary(1,1)+13,metric_string,'Color','y',...
     'FontSize',14,'FontWeight','bold');

end

end