Chain codes

Chain codes

Published by: Neha Khadka

Published date: 29 Jul 2024

Chain codes

Pattern Recognition

The identification and classification of patterns in data is the primary emphasis of the machine learning and artificial intelligence field of pattern recognition. It entails the process of categorizing incoming data according to important characteristics or patterns into objects or classes. Text, sounds, pictures, and signals are just a few of the many data kinds to which this approach can be used.

Chain Codes

In image processing and computer vision, chain codes are a technique used to describe an object's border in a digital image. By encoding the orientations of the border segments, they are able to characterize the geometry of a boundary. An introduction to chain codes and their uses is provided below:

How Chain Codes Work

  • Boundary Detection: First, the boundary of the object in the image is detected. This is usually done through edge detection algorithms.
  • Starting Point: Select a starting point on the boundary.
  • Direction Encoding: Move along the boundary in a consistent direction (e.g., clockwise) and record the direction of each segment using a predefined code. Commonly used directions are based on 4-connectivity or 8-connectivity:
  • 4-connectivity: Uses 4 possible directions (up, right, down, left).
  • 8-connectivity: Uses 8 possible directions (up, up-right, right, down-right, down, down-left, left, up-left).

Example of Chain Codes

For 4-connectivity, the directions might be encoded as:

  • 0: Right
  • 1: Up
  • 2: Left
  • 3: Down

For 8-connectivity, the directions might be encoded as:

  • 0: Right
  • 1: Up-right
  • 2: Up
  • 3: Up-left
  • 4: Left
  • 5: Down-left
  • 6: Down
  • 7: Down-right

Applications

  • Shape Analysis: Chain codes are used to analyze the shape of objects in images.
  • Pattern Recognition: Useful in pattern recognition tasks where the shape or contour of an object is a key feature.
  • Image Compression: Can be used for compressing the representation of object boundaries.
  • Object Tracking: Helpful in tracking the movement of objects by following their boundaries.