Unsigned Manhattan chain code

• A new chain code named Unsigned Manhattan Chain Code (UMCC) is presented.
• UMCC is insensitive to rotation and mirroring, and enables shape magnification.
• UMCC is capable of detecting monotone parts of the shape’s boundary.
• The proposed chain code achieves 50% better compression ratio than F8 code.

This paper introduces a new chain code named Unsigned Manhattan Chain Code – UMCC. Although it exploits a pixel’s neighbourhood of 8-connectivity, only two coding symbols are used for navigating through the geometric shape’s boundary pixels. For this, the movements in the xx- and yy-coordinate direction are separated, whilst the sign of the moving direction is controlled by two flags – one for each coordinate direction. UMCC is insensitive to rotation and mirroring and enables shape magnification. However, the more unique property is the UMCC’s ability to explicitly separate the monotonic parts of the geometric shape. UMCC’s properties have been compared against the properties of other chain codes including the Freeman chain code in eight and four directions, the Vertex Chain Code, and the Three OrThogonal chain code. It has been shown that the UMCC has superior properties in regards to the up-to-date chain codes.