How to find the center position under the saturation spot signal

Hello, I would like to seek your help. I have an image below. How can I find the spot position centre (X,Y) under the saturation spot signal?

The code as below

clear all; close all;clc

D = 'C:\Users\Admin\Desktop';
S = dir(fullfile(D,'*.bmp')); % pattern to match filenames.

%%-------open  file----
    S_BG = dir(fullfile(D,'figure.bmp')); % pattern to match filenames.
    for k_BG = 1:numel(S_BG)
        F_BG = fullfile(D,S_BG(k_BG).name);
        I_BG = imread(F_BG);
         
        Z = im2double(I_BG);
         Z = rgb2gray(Z);
       
        figure(100),imshow(Z)
        figure(101)
        surf(Z)     
    end

Answer 1

[Steve Eddins]

Try converting the image to binary using imbinarize and then using regionprops to compute the centroid.

rgb = imread('image.bmp');
I = rgb2gray(rgb);
bw = imbinarize(I);
s = regionprops(bw,'Centroid')

s = struct with fields:
    Centroid: [202.0826 195.7218]

imshow(I,'InitialMagnification','fit')
hold on
plot(s.Centroid(1),s.Centroid(2),'b*')
hold off

Alternatively, consider computing a weighted centroid using the grayscale pixel values. First, expand the binarized object using dilation to include more of the grayscale pixel values at the edge of the object.

bw2 = imdilate(bw,strel('disk',20));
s2 = regionprops(bw2,I,'WeightedCentroid')

s2 = struct with fields:
    WeightedCentroid: [202.0307 195.3167]

imshow(I,'InitialMagnification','fit')
hold on
plot(s2.WeightedCentroid(1),s2.WeightedCentroid(2),'b*')
hold off

[Tina Hsiao]

Thanks a lot.