How to mask an image?

hi I have the following code: I want to apply a mask on the image.. How I could ???

I1 = imread('eye.jpg');
figure (1)
 imshow(I1)
 figure(2)
binaryimage=I1>=20 & I1 <=255;
imshow(binaryimage, []);
title('binaryimage 1// Gray');

Answer 1

[Image Analyst]

See several of my demos attached below (in blue).

[Christine Ak]

Thxxx Alot :D :D