CCITT two-dimensional

Understanding CCITT Two-Dimensional Coding: A Deep Dive into Modified Relative Element Address Designation

The CCITT (International Telegraph and Telephone Consultative Committee) two-dimensional coding scheme, also known as Modified Relative Element Address Designation (MREAD), offers an efficient way to represent changes in a two-dimensional image or data structure. This approach is particularly useful in situations where the changes between lines are relatively small and localized.

How It Works:

MREAD utilizes a reference line, typically located directly above the current line, to encode the position of changing elements. The code for each changing element on the current line is determined by its relative position to:

1. The changing element on the reference line: This applies if the changing element on the current line has a counterpart on the reference line. The code represents the horizontal distance between the two elements.
2. The preceding changing element on the current line: This is used if the changing element doesn't have a direct counterpart on the reference line. The code indicates the horizontal distance from the previous changing element on the current line.

Advantages of CCITT Two-Dimensional Coding:

• Efficient Representation: MREAD significantly reduces the amount of data needed to represent an image, particularly when the image contains areas of low complexity or gradual changes.
• Simplicity and Ease of Implementation: The coding logic is straightforward and can be easily implemented in hardware or software.
• Minimal Overhead: The reference line only needs to be stored once, and the codes for changing elements are relatively compact.

Example:

Imagine a simple black and white image where the reference line (above) is represented by the sequence "010010" and the current line is "011010". The changing elements on the current line are at positions 2 and 3, which correspond to the changing elements on the reference line.

Using MREAD, the code for the changing element at position 2 would be "0" (as it's the same position as on the reference line). The code for the changing element at position 3 would be "1" (as it is one position to the right of the corresponding element on the reference line).

Applications of CCITT Two-Dimensional Coding:

MREAD finds its application in various fields, including:

• Image Compression: It's used in fax machines and other image compression techniques to efficiently transmit images.
• Data Transmission: The scheme helps reduce the data volume required for transmitting line drawings and other graphic data.
• Document Scanning: It plays a role in scanning documents, where differences between consecutive lines are often minimal.

Conclusion:

CCITT two-dimensional coding, with its MREAD approach, is a valuable tool for representing data efficiently. By exploiting the correlation between consecutive lines, it minimizes the amount of data needed to transmit or store images and other information. This makes it a valuable technique in various applications requiring efficient data handling and transmission.