3. Introduction
• Chain code is a technique used in digital image processing for contour
detection..
• Contours play a crucial role in various applications, such as object
recognition, shape analysis, and image segmentation.
4. Contour Detection
• Contour detection is the process of identifying and extracting the boundaries
of objects in an image.
• It is an essential step in many image processing and computer vision tasks.
• The accurate detection of contours helps in segmenting objects from the
background and analyzing their shapes and structures.
5.
6. Chain Code Overview
• Chain code is a method for representing contours by encoding the sequence
of connected pixels along the contour.
• It provides a compact representation of the shape of an object.
• Chain code follows the boundary of an object, pixel by pixel, starting from a
chosen point on the contour.
7. 4-Connected Chain Code
• 4-connected chain code considers only four neighboring pixels around the
current pixel (top, right, bottom, and left).
• It assigns a unique number (0 to 3) to each direction, representing the
direction from the current pixel to the next pixel on the contour.
• The chain code is generated by tracing the boundary of an object using these
directional numbers.
8. 8-Connected Chain Code
• 8-connected chain code considers eight neighboring pixels around the
current pixel (top-left, top, top-right, right, bottom-right, bottom, bottom-
left, and left).
• The chain code assigns a unique number (0 to 7) to each direction,
representing the direction from the current pixel to the next pixel on the
contour.
• The chain code is generated by tracing the boundary of an object using these
directional numbers.
9.
10.
11. The First Difference of a Chain Codes
• Problem of a chain code:
• chain code sequence depends on a starting point.
• Solution:
• treat a chain code as a circular sequence and redefine the starting point so that the
resulting sequence of numbers forms an integer of minimum magnitude.
• The first difference of a chain code:
• counting the number of direction change (in counterclockwise) between 2 adjacent
elements of the code.
12.
13. Applications of Chain Code
• Chain code has various applications in image processing and computer
vision.
• It is used for contour matching, where the chain codes of two contours are
compared to determine their similarity.
• Object recognition, where the contour shape is analyzed for identifying and
categorizing objects.
• Shape analysis techniques rely on chain code for quantifying and comparing
object
14. Advantages of Chain Code
• Chain code offers a compact representation of contours, reducing the
storage and computational requirements.
• It is invariant to rotation, as the encoding of the contour does not depend
on the orientation of the object.
• Chain code is relatively simple to implement and can be computed efficiently.
15. Limitations of Chain Code
• Chain code representation can be sensitive to noise, as noise pixels may
introduce deviations in the contour.
• It may result in loss of detail in the representation, particularly for complex
or highly detailed contours
16. Conclusion
• Chain code is a valuable tool for analyzing and understanding the shapes and
structures of objects in digital images.
