I have a rectangular image. I want to crop the AOI which is circular. Please guide me how to do it. I have attached the image here. It is an all sky image.

I have a rectangular image. I want to crop the AOI which is circular. I want to define a suitable radius and only tat part has to be retained.

Answer 1

[Image Analyst]

Create a circular mask like in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F

Then you can multiply it by the image or use it as an index to zero out pixels:

grayImage(circlePixels) = 0;