Detecting Cold Area in My Thermal Image

Hello there, I have the image attached. It was taken with FLIR E5 I need to extract the blue area only for the purpose of detecting the defects. I have tried several ways but they are all not working with me unfortunately :(

Can any one help me here ??

Answer 1

[KSSV]

I = imread('FLIR0072.jpg') ;
I1 = rgb2gray(I) ;
[y,x] = find(I1<=15) ;

imshow(I)
hold on
plot(x,y,'.r')

[Tasneem Al-Tmimi]

Thank you, but what is 15 in

find(I1<=15)

[Tasneem Al-Tmimi]

Actually it is not always working :)

But thank you