1 Executive Summary
- JPEG 2000 is a new digital imaging system that builds on JPEG but differs from it.
- It utilizes a wavelet transform and an arithmetic coding scheme to achieve 'scalability' in its design and operation.
- It offers improved compression - better quality for a given file size, or smaller file size for a given quality - under most circumstances. This is especially true at very high compression.
- In exchange for better performance it is significantly more complex; typically it requires more processor cycles and more memory resources for equivalent tasks.
- At high compression, JPEG 2000 exhibits different kinds of typical compression artefacts to those of JPEG and to other compression systems.
- Typical existing JPEG imagery can be transcoded to JPEG 2000 and very close quality maintained without an increase in file size.
- JPEG 2000 can utilize a single algorithm to encode images both losslessly (exactly) and lossily (inexactly). The original JPEG is lossy only.
- A single JPEG 2000 file, for example losslessly encoded, can be used efficiently to generate multiple versions for multiple applications. These might include versions with different behaviours during progressive display, and versions with different degrees of compression - for example, much smaller, lossy versions. The efficiency with which such transcoding can be done with JPEG 2000 makes it feasible for only the source image to be stored permanently.
- This 'scalability' enables JPEG 2000 images to be additionally compressed without intermediate decoding, for example to free up disk space.
- JPEG 2000 supports the preferential encoding of 'regions of interest' in various ways. A region of interest may be encoded with higher quality or so that it appears earlier than the rest of the image during progressive display.
- All of the core functionality of JPEG 2000 is defined in Part 1 of the standard ISO/IEC 15444. This includes an official file format called JP2.
- It is intended that JPEG 2000 Part 1 should be implemented without the payment of licence fees or royalties. Many patent holders have waived their rights to this effect. However, as in any other case, implementers are ultimately responsible for ensuring that no patents are infringed.
- JPEG 2000 Part 4 addresses the testing of conformance to Part 1. JPEG 2000 Part 5 includes two software implementations. Other parts of the standard define extensions of various kinds.
- The JPEG 2000 file format supports the integration of image metadata with the image, and particularly encourages the use of XML for metadata.
- Modern colour management is also built into the JPEG 2000 file format.
- There are several extended file formats, called JPX, MJ2 and JPM; all belong to the same family as JP2. MJ2 is specifically for motion, and JPM for document imaging.
- Some of the extended formats support fragmentation of data over a network, in a 'virtual' file. Basic support for cryptographic and verification technology is also provided.
- Adoption of JPEG 2000 in the marketplace is growing and expected to continue.