How to detect bright spot on image?

How find coordinates bright spot and placed dot on this? please could you help me

For example, we have pic(attach.) and need find centre this figure(centre of the image and centre of the figure on image its diffrent things, because they could be shifted relatively each other), we need find ROI with max intensity, who contained ~90%(10% is a noise and e.t.c.) all intensity. ROI containing max intensity include centre of the figure who i need to find. How i can do this? help me please.

(sorry for my bad English)

[Yaroslav Gimler]

i find centre of mass, but that's not what me need

[Yaroslav Gimler]

bump

[KSSV]

Attach the original image without a mark at the center. So that users can work on the image.

Answer 1

[KSSV]

I = imread('11.JPG') ;
I1 = rgb2gray(I) ;
[y,x] = find(I1==255) ;
%% Fit circle to the data (x,y)
n=length(x);  xx=x.*x; yy=y.*y; xy=x.*y;
A=[sum(x) sum(y) n;sum(xy) sum(yy) sum(y);sum(xx) sum(xy) sum(x)];
B=[-sum(xx+yy) ; -sum(xx.*y+yy.*y) ; -sum(xx.*x+xy.*y)];
a=A\B;
% Center of cricle 
xc = -.5*a(1);
yc = -.5*a(2);
R  =  sqrt((a(1)^2+a(2)^2)/4-a(3));
% Plot 
imshow(I)
hold on
plot(xc,yc,'*b')

Instead of fitting a circle, you can straight away, use mean of x and y also.

[Yaroslav Gimler]

Thank you very much! KSSV

[KSSV]

happy to help you...enjoy matlab.

KSSV

B,C,J,I

[Yaroslav Gimler]

I have one more question about region of inerests on this pic, where wiil be max intesity. How i can do it? Itry with this code, but it didnt work.

My code:

I = imread('1.JPG') ;
I1 = rgb2gray(I) ;
maxI = max(max(I1));
porog = 0.1 * maxI;
[ycenter, xcenter] = find(I1 == maxI) ;
[y, x] = find(I1 >= porog) ;
I2 = I1(ycenter - (max(y) - ycenter) : max(y), min(x) : max(x));
figure, imshow(I2)

Could you help me again? Thank you!

[Image Analyst]

xcenter and ycenter are the locations of the max value in your gray scale image.

x and y ARE NOT the locations of the maxima in the binary image "I1>porog". They are the rows and columns an any/every pixel that is above the threshold of porog.

I2 appears to be some sort of attempt at cropping but I'm not sure what you're trying to achieve with that code.

[Yaroslav Gimler]

>I2 appears to be some sort of attempt at cropping but I'm not sure what you're trying to achieve with that code.

I trying cropp area where value will be maximum and cut out unnecessary areas. I need area only conoscopic cross without black background and other things.

I will try to show what I need on the attached picture.

[Image Analyst]

You say, quoting: "I have one more question about region of inerests on this pic, where wiil be max intesity. How i can do it?" but you don't actually say what "it" IS. What is "it"? What do you want to do? Just crop some number of rows and columns from the centroid?

[Yaroslav Gimler]

I have an image. In this image there is a conoscopic cross, the center of the image and the center of the conoscopic cross are different things. I understood how to find the center of the conoscopic cross, but now I have to select the conoscopic cross itself and remove the unnecessary. For example, the entire image has 100% intensity, and the conoscopic cross is 90% (10% is background and noise).I need to leave only these 90% where we have a conoscopic cross.How to do this is hard for me to imagine.

Sorry for my bad english.

[Image Analyst]

Just do

halfWindowWidth = 100;  % Whatever size you want.
% row1 = round(yCentroid - halfWindowWidth);
row2 = row1 + 2 * halfWindowWidth - 1;
col1 = round(xCentroid - halfWindowWidth);
col2 = col1 + 2 * halfWindowWidth - 1;
croppedImage = rgbImage(row1:row2, col1:col2, :)

Answer 2

[Image Analyst]

You could do it based on just the largest blob, which will be at the center.

binaryImage = bwareafilt(binaryImage, 1); % Extract largest blob.
props = regionprops(binaryImage, 'Centroid'); % Find centroid (not weighted by gray level).
xCentroid = props.Centroid(1);
yCentroid = props.Centroid(2);
hold on;
plot(xCentroid, yCentroid, 'b+', 'MarkerSize', 50); % Plot cross over centroid.

[Yaroslav Gimler]

>bwareafilt

>Introduced in R2014b

I cant use this function, because i have Matlab R2012b version.

[Image Analyst]

Use bwareaopen() instead.

Better yet, upgrade to R2018b since your version is 6 years old.