how can i paste a cropped head of one image into another?

I have cropped the head of the cameraman.jpeg using circular crop and have embedded watermark in it. Now i need to place this embedded head into the original cameraman.jpeg. How can i do this?

Answer 1

[David Sanchez]

I = imread('cameraman.tif');
head = I( (35:85),(100:140) ); % crop of the head

% code to transform head here

I( (35:85),(100:140) ) = modified_head;

Answer 2

[as825]

actually the above code is for a normal cropping and i need it for circular cropping. The description of the problem is stated above in the description part..