Difference Chain Codes
The difference chain codes can be computed by counting (counterclockwise) the number of directions that separate two adjacent elements of the code [7]. This operation allows us to rotate the object in 90-degree increments and still have the same difference chain code.
Example: If the chain code of the object is 0 1 1 2 2 3 0 3. the difference code of this code is 1 0 1 0 1 1 3 1.