How can I accurately plot the centroid of black dots in MATLAB?

I have an Image in which I am trying to determine the centroid of the black dots. My Code seems to have trouble recognizing the centroid for all black dots as their respective shade of grey differs. Would anyone be able to guide me into how I could diagnose this? Thank you!

%%Centroid 

clear,clc

grid on
X = imread('redbox_5.bmp');
figure
imagesc(X)

se = strel('disk',3);

J = imsubtract(imadd(X,imtophat(X,se)),imbothat(X,se));
figure
imshow(J)

newmap2 = contrast(J,2);
colormap(newmap2)

figure(2);imshow(J);
%grey point less than 30
BW=J<30;
%Find Weighted Centroid of the chosen dots and plot them together with original image
%https://www.mathworks.com/matlabcentral/answers/332938-how-to-identify-black-dots-using-matlab

   rp=regionprops(BW,J,'WeightedCentroid');
        n=numel(rp);
           for j=1:n
               Position(j,1)=rp(j).WeightedCentroid(1);
               Position(j,2)=rp(j).WeightedCentroid(2);
           end

   for i=1:n-1
           if  (Position(i+1,1)-Position(i,1))<5 || (Position(i+1,2)-Position(i,2))<5
               Position(i+1,1)=1/2*(Position(i,1)+Position(i+1,1));
               Position(i+1,2)=1/2*(Position(i,2)+Position(i+1,2));
               Position(i,1)=0;Position(i,2)=0;
           end
           end
      [m,n]=size(Position);
      figure(3);imshow(J); axis image; hold on;
          for i=1:m
            for j=1:n-1
            plot(Position(i,j),Position(i,j+1),'r*')
            end
          end
       Position(all(Position==0,2),:)=[];
       display(Position);

Answer 1

[Anton Semechko]

% Get the image
im=imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/120388/MATLAB_QUESTION.PNG');
im=max(im,[],3);

% Segment blobs
bw=imclose(im<60,strel('disk',5));

% Cenroids of individual blobs
RP=regionprops(bw,'Centroid');
N=numel(RP);
C=zeros(N,2);
for i=1:N, C(i,:)=RP(i).Centroid; end

% Centroid of all blobs
C_net=regionprops(double(bw),'Centroid');
C_net=C_net.Centroid;

figure
imshow(bw)
hold on
plot(C(:,1),C(:,2),'or','MarkerSize',10,'LineWidth',2)
plot(C_net(:,1),C_net(:,2),'*g','MarkerSize',10,'LineWidth',2)

[Image Analyst]

I wouldn't call imclose(). That changes the shape and possibly moves the centroids. If there are noise pixels, I'd call imfill() and then bwareafilt(binaryImage, 4).

[PamunkeBoy]

Thank you all for your help!

[PamunkeBoy]

Image Analyst, I was having trouble with the bwareafilt function. What is it supposed to do?

[Image Analyst]

It

(1) removes blobs that are not in the range (2 numbers) you specify, or

(2) removes or keeps the N largest or smallest blobs if you pass in a single number.

[PamunkeBoy]

Okay. I was also having trouble coding with imclose(). How am I supposed to code this?