How can I separate a section of a graph with high values or Energy?

In the image that I have attached to this question I would like to write a code to separate the values between the two data cursor from the rest of the data. How can I do that?

[KSSV]

You have both x and y data to plot or you have plotted only y w.r.t indices.

[Kian Azami]

I have only y with respect to the indices. However I can have the values of x which is not very important for me. The y is the intensity of each pixel color, and the x is the pixels positions. Therefore values of y with high intensity is the position where my image occurs and I want to separate it from the rest of the image.

Answer 1

[KSSV]

If you have only y and plotting wrt indices then:

iwantx=416:1188;
iwant=y(I want);

If you have both x and y data.

iwantx=x(x>=416 & x<=1188) ;
iwanty=y(x>=416 & x<=1188) ;

[Kian Azami]

No the point is that I have many images and I want to find them automatically by programming. Not just by open the image and look at the indices. I want to find a way to find these indices automatically.

[KSSV]

You fix a threshold intensity value and pick y values greater then this threshold.

[Kian Azami]

This can be a good Idea! However sometimes there are noises that goes beyond that threshold but they are thin respect to the interested area. Maybe I can put a threshold and then I should put another condition with respect to the width?

[KSSV]

One intensity threshold intensity is enough....you try out for one and check.