A chain code is a

lossless compression Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statisti ...

based

image segmentation In digital image processing and computer vision, image segmentation is the process of partitioning a digital image into multiple image segments, also known as image regions or image objects ( sets of pixels). The goal of segmentation is to simpli ...

method for

binary image A binary image is one that consists of pixels that can have one of exactly two colors, usually black and white. Binary images are also called ''bi-level'' or ''two-level'', Pixelart made of two colours is often referred to as ''1-Bit'' or ''1b ...

s based upon tracing image contours. The basic principle of chain coding, like other contour codings, is to separately encode each connected component, or "blob", in the image. For each such region, a point on the boundary is selected and its coordinates are transmitted. The encoder then moves along the boundary of the region and, at each step, transmits a symbol representing the direction of this movement. This continues until the encoder returns to the starting position, at which point the blob has been completely described, and encoding continues with the next blob in the image. This encoding method is particularly effective for images consisting of a reasonably small number of large connected components.

Variations

Some popular chain codes include: * the

Freeman Freeman, free men, or variant, may refer to: * a member of the Third Estate in medieval society (commoners), see estates of the realm * Freeman, an apprentice who has been granted freedom of the company, was a rank within Livery companies * Free ...

Chain Code of Eight Directions (FCCE) * Directional

Chain Code of Eight Directions (DFCCE) * Vertex Chain Code (VCC) * Three OrThogonal symbol chain code (3OT) * Unsigned Manhattan Chain Code (UMCC) * Ant Colonies Chain Code (ACCC) * Predator-Prey System Chain Code (PPSCC) * Beaver Territories Chain Code (BTCC) * Biological Reproduction Chain Code (BRCC) * Agent-Based Modeling Chain Code (ABMCC) In particular, FCCE, VCC, 3OT and DFCCE can be transformed from one to another Abstract Cell Coordinate Oriented Crack Code

Abstract Cell Coordinate Oriented Crack Code

A related blob encoding method is crack code. Algorithms exist to convert between chain code, crack code, and run-length encoding. A new trend of chain codes involve the utilization of biological behaviors. This started by the work of Mouring et al. who developed an algorithm that takes advantage of the pheromone of ants to track image information. An ant releases a pheromone when they find a piece of food. Other ants use the pheromone to track the food. In their algorithm, an image is transferred into a virtual environment that consists of food and paths according to the distribution of the pixels in the original image. Then, ants are distributed and their job is to move around while releasing pheromone when they encounter food items. This helps other ants identify information, and therefore, encode information.

In use

Recently, the combination of

move-to-front transform The move-to-front (MTF) transform is an encoding of data (typically a stream of bytes) designed to improve the performance of entropy encoding techniques of compression. When efficiently implemented, it is fast enough that its benefits usually ...

and adaptive

run-length encoding Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original ...

accomplished efficient compression of the popular chain codes. Chain codes also can be used to obtain high levels of compression for image documents, outperforming standards such as

DjVu DjVu ( , like French " déjà vu") is a computer file format designed primarily to store scanned documents, especially those containing a combination of text, line drawings, indexed color images, and photographs. It uses technologies such as im ...

and

JBIG2 JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. It is suitable for both lossless and lossy compression. According to a press release from the Group, in its lossless mode JBIG2 ty ...

References

{{Compression methods Lossless compression algorithms Image compression

Variations

In use

See also

References