The LOCO-I lossless image compression algorithm: principles and standardization into JPEG-LS

Area of Science:

• Computer Science
• Image Processing
• Data Compression

Background:

• Existing lossless image compression methods often involve high computational complexity.
• The need for efficient and effective compression algorithms for continuous-tone images is critical in digital imaging.

Purpose of the Study:

• To introduce and explain the LOCO-I algorithm, the core of the JPEG-LS standard.
• To highlight the design principles that enable low complexity and high compression performance.
• To discuss the successful standardization of LOCO-I into JPEG-LS.

Main Methods:

• Utilizing a low complexity projection of universal context modeling.
• Employing a simple fixed context model to capture high-order dependencies.
• Integrating adaptively chosen Golomb-type codes and alphabet extension for efficient coding.

Main Results:

• LOCO-I achieves compression ratios similar or superior to state-of-the-art arithmetic coding schemes.
• The algorithm demonstrates performance within a few percentage points of the best available compression ratios.
• Significantly lower complexity compared to existing high-performance compression techniques.

Conclusions:

• LOCO-I offers a compelling balance of compression efficiency and low computational complexity.
• Its integration into the JPEG-LS standard provides a practical solution for lossless continuous-tone image compression.
• The algorithm's design represents a significant advancement in efficient image compression technology.