How to crop only a region that is surrounded by a boundary

I am working on sign boards detection.Want to crop region surrounded by red circle boundary so i can compare with standard imag.Can anybody help me with the steps or code for it

[Walter Roberson]

http://www.mathworks.co.uk/matlabcentral/answers/43073-a-guide-to-tags

Answer 1

[KSSV]

doc imcrop. https://in.mathworks.com/help/images/ref/imcrop.html

Answer 2

[Walter Roberson]

First you need to detect the red pixels to create a binary image whose pixels are set at the red. Next imfill() to fill the holes. Now zero the locations where the boundary was, to remove the place the red pixels themselves were. What remains is a mask of the locations inside the circle.

You can then use regionprops to find the bounding box, and then you can use that bounding box to crop using the imcrop that KSSV recommends.