How to remove a region of an image using thresholding?

I want to remove a background of the image using to thresholding.My image is a x-ray image and i am using Matlab R2018a. I am attaching my image here.I want to seperate skull part from the background. Can you please suggest any code or solution?

Answer 1

[KALYAN ACHARJYA]

This work relates to image segmentation. you can do it in multiple ways, for perfection results you have to try with different methods. I suggest you read the Image Segmentation chapter in Digital Image Processing (Gonzalez Book). You can apply different ways, local thresholding or global thresholding depending on your required results (read about Otsu's Thresholding technique)

The Easiest way you can proceed as followings-

gray_im=rgb2gray(imread('055_edited.bmp'));
subplot(121);imshow(gray_im)  % Decide the threshold as requirement of your results
threshold1=gray_im>100;
subplot(122);imshow(threshold1);

% Perform some morphological operations to remove all extra parts

[Nayana R]

Thank you so much for your reply.here I want to remove the border area and seperate skull.Can you please suggest a method for seperating border and to get the skull for black background?