Select ROI from an image

my question is i need to get a region of interest first on the image, the shown code can crop an image manually, but i prefer it to be cropping with fixed size. please helpre

[Geoff Hayes]

Shweta - do you have access to the Image Processing Toolbox or are you hoping to write your own code to do this for you?

[Walter Roberson]

Please read https://www.mathworks.com/matlabcentral/answers/243406-how-scan-an-image-fully-and-seperate-the-area-of-interest-using-matlab#answer_192657