how to imcrop function customize without selecting a rectangular region ?

Could you please explain how to select a particular object of a image without selecting a rectangular region.

for eg:

smallSubImage = imcrop(rgbImage, [120, 250, templateWidth, templateHeight]);

I referred the below previous work of Matlab

https://in.mathworks.com/matlabcentral/answers/uploaded_files/59541/normxcorr2_demo.m

[Gopichandh Danala]

What is the expected region if not a rectangle, do you want a manually cropped shape?