How to make chain code starting point invariant?

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I am using chain code as a feature extraction techniques. I have been able to extract chain code of the required object. However I have seen in some research papers that chain code can be made to be starting point invariant?

The chain code is highly dependent on the starting point • To reduce this dependency we regard the code as a circular number with n numerals. By finding the 1 ≤ i ≤ n that yields the lowest number when the chain code is read like a ordinary number we obtain a code that is invariant to starting point

How can i implement it? Can someone guide me?