JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding their original JPEG standard (created in 1992), which is based on a discrete cosine transform (DCT), with a newly designed, wavelet-based method. The standardized filename extension is .jp2 for ISO/IEC 15444-1 conforming files and .jpx or .jpf for the extended part-2 specifications, published as ISO/IEC 15444-2. The MIME types for JPEG 2000 are defined in RFC 3745. The MIME type for JPEG 2000 (ISO/IEC 15444-1) is image/jp2.
The JPEG 2000 project was motivated by Ricoh's submission in 1995 of the CREW (compression with reversible embedded wavelets) algorithm to the standardization effort of JPEG LS. Ultimately the LOCO-I algorithm was selected as the basis for JPEG LS, but many of the features of CREW ended up in the JPEG 2000 standard.
JPEG 2000 codestreams are regions of interest that offer several mechanisms to support spatial random access or region of interest access at varying degrees of granularity. It is possible to store different parts of the same picture using different quality.
JPEG 2000 is a compression standard based on a discrete wavelet transform (DWT). The standard could be adapted for motion imaging video compression with the Motion JPEG 2000 extension. JPEG 2000 technology was selected as the video coding standard for digital cinema in 2004. However, JPEG 2000 is generally not supported in web browsers for web pages and hence is not generally used on the World Wide Web. Nevertheless, for those with PDF support, web browsers generally support JPEG 2000 in PDFs.
Unlike the legacy .jpg format, which offers basic image compression without support for embedded metadata or access control, JPEG 2000 introduces advanced container options such as .jp2 and .jpf. Of these, the .jpf extension offers a significantly more powerful and extensible framework. It supports high-fidelity wavelet compression, layered and tiled image structures, region-of-interest encoding, and remote streaming via the JPEG 2000 Interactive Protocol (JPIP).
The .jpf extension can be used to embed machine-readable consent flags, secure face hashes, and cryptographic signatures. This format can be used along with JPIP for time-limited, revocable access to visual data.
Design goals While there is a modest increase in compression performance of JPEG 2000 compared to JPEG, the main advantage offered by JPEG 2000 is the significant flexibility of the codestream. The codestream obtained after compression of an image with JPEG 2000 is scalable in nature, meaning that it can be decoded in a number of ways; for instance, by truncating the codestream at any point, one may obtain a representation of the image at a lower resolution, or signal-to-noise ratio – see scalable compression. By ordering the codestream in various ways, applications can achieve significant performance increases. However, as a consequence of this flexibility, JPEG 2000 requires codecs that are complex and computationally demanding. Another difference, in comparison with JPEG, is in terms of visual artifacts: JPEG 2000 only produces ringing artifacts, manifested as blur and rings near edges in the image, while JPEG produces both ringing artifacts and 'blocking' artifacts, due to its 8×8 blocks.
JPEG 2000 has been published as an ISO standard, ISO/IEC 15444. The cost of obtaining all documents for the standard has been estimated at 2,718CHF (US$2,720 as of 2015).
Applications Notable markets and applications intended to be served by the standard include: Consumer applications such as multimedia devices (e.g. digital cameras, personal digital assistants, 3G mobile phones, color facsimile, printers, scanners) Client/server communication (e.g. the Internet, image database, video streaming, video server) Military/surveillance (e.g. HD satellite images, Motion detection, network distribution and storage) Medical imagery, specifically the DICOM specifications for medical data interchange. Biometrics Remote sensing High-quality frame-based video recording, editing and storage. Live HDTV feed contribution (I-frame only video compression with low transmission latency), such as live HDTV feed of a sport event linked to the TV station studio Digital cinema, such as Digital Cinema Package Digitized Audio-visual contents and images for long term digital preservation World Meteorological Organization has built JPEG 2000 Compression into the new GRIB2 file format. The GRIB file structure is designed for global distribution of meteorological data. The implementation of JPEG 2000 compression in GRIB2 has reduced file sizes up to 80%.wgrib2 home page
Improvements over the 1992 JPEG standard
Multiple resolution representation JPEG 2000 decomposes the image into a multiple resolution representation in the course of its compression process. This pyramid representation can be put to use for other image presentation purposes beyond compression.
Progressive transmission by pixel and resolution accuracy These features are more commonly known as progressive decoding and signal-to-noise ratio (SNR) scalability. JPEG 2000 provides efficient codestream organizations which are progressive by pixel accuracy and by image resolution (or by image size). This allows the viewer to see a lower quality version of the final picture before the whole file has been downloaded. The quality improves progressively as more data is downloaded from the source.
Choice of lossless or lossy compression Like the Lossless JPEG standard,The JPEG Still Picture Compression Standard pp.6–7 the JPEG 2000 standard provides both lossless and lossy compression in a single compression architecture. Lossless compression is provided by the use of a reversible integer wavelet transform in JPEG 2000.
Flexible file format The JP2 and JPX file formats allow for handling of color-space information, metadata, and for interactivity in networked applications as developed in the JPEG Part 9 JPIP protocol.
High dynamic range support JPEG 2000 supports bit depths of 1 to 38 bits per component. Supported color spaces include monochrome, 3 types of YCbCr, sRGB, PhotoYCC, CMY(K), YCCK and CIELab. It also later added support for CIEJab (CIECAM02), e-sRGB, ROMM, YPbPr and others.
Side channel spatial information Full support for transparency and alpha planes.
JPEG 2000 image coding system – Parts The JPEG 2000 image coding system (ISO/IEC 15444) consists of the following parts:
+ JPEG 2000 image coding system – Parts Part Number public release date Latestamend-ment IdenticalITU-Tstandard Title Description Firstedition Currentedition Part 1 ISO/IEC 15444-1 2000 2024 T.800 Core coding system the basic characteristics of JPEG 2000 compression (.jp2) Part 2 ISO/IEC 15444-2 2004 2023 T.801 Extensions (.jpx, .jpf, floating points) Part 3 ISO/IEC 15444-3 2002 2007 2010 T.802 Motion JPEG 2000 (.mj2) Part 4 ISO/IEC 15444-4 2002 2024 T.803 Conformance testing Part 5 ISO/IEC 15444-5 2003 2021 T.804 Reference software Java and C implementations Part 6 ISO/IEC 15444-6 2003 2013 T.805 Compound image file format (.jpm) e.g. document imaging, for pre-press and fax-like applications Part 7 abandoned Guideline of minimum support function of ISO/IEC 15444-1 (Technical Report on Minimum Support Functions) Part 8 ISO/IEC 15444-8 2007 2023 T.807 Secure JPEG 2000 JPSEC (security aspects) Part 9 ISO/IEC 15444-9 2005 2023 T.808 Interactivity tools, APIs and protocols JPIP (interactive protocols and API) Part 10 ISO/IEC 15444-10 2008 2011 T.809 Extensions for three-dimensional data JP3D (volumetric imaging) Part 11 ISO/IEC 15444-11 2007 2007 2013 T.810 Wireless JPWL (wireless applications) Part 12 ISO/IEC 15444-12(withdrawn in 2017) 2004 2015 ISO base media file format Part 13 ISO/IEC 15444-13 2008 2008 T.812 An entry-level JPEG 2000 encoder Part 14 ISO/IEC 15444-14 2013 T.813 XML representation and reference JPXML Part 15 ISO/IEC 15444-15 2019 2019 T.814 High-throughput JPEG 2000 HTJ2K and JPH file format Part 16 ISO/IEC 15444-16 2019 2025 T.815 Enhanced encapsulation of JPEG 2000 images into ISO/IEC 14496-12 HEIF
Technical discussion The aim of JPEG 2000 is not only improving compression performance over JPEG but also adding (or improving) features such as scalability and editability. JPEG 2000's improvement in compression performance relative to the original JPEG standard is actually rather modest and should not ordinarily be the primary consideration for evaluating the design. Very low and very high compression rates are supported in JPEG 2000. The ability of the design to handle a very large range of effective bit rates is one of the strengths of JPEG 2000. For example, to reduce the number of bits for a picture below a certain amount, the advisable thing to do with the first JPEG standard is to reduce the resolution of the input image before encoding it. That is unnecessary when using JPEG 2000, because JPEG 2000 already does this automatically through its multi-resolution decomposition structure. The following sections describe the algorithm of JPEG 2000.
According to the Royal Library of the Netherlands, "the current JP2 format specification leaves room for multiple interpretations when it comes to the support of ICC profiles, and the handling of grid resolution information".
Color components transformation Initially images have to be transformed from the RGB color space to another color space, leading to three components that are handled separately. There are two possible choices: Irreversible Color Transform (ICT) uses the well known BT.601 YCC color space. It is called "irreversible" because it has to be implemented in floating or fix-point and causes round-off errors. The ICT shall be used only with the 9/7 wavelet transform. Reversible Color Transform (RCT) uses a modified YUV color space (almost the same as YCC) that does not introduce quantization errors, so it is fully reversible. Proper implementation of the RCT requires that numbers be rounded as specified and cannot be expressed exactly in matrix form. The RCT shall be used only with the 5/3 wavelet transform. The transformations are:
If R, G, and B are normalized to the same precision, then numeric precision of C and C is one bit greater than the precision of the original components. This increase in precision is necessary to ensure reversibility. The chrominance components can be, but do not necessarily have to be, downscaled in resolution; in fact, since the wavelet transformation already separates images into scales, downsampling is more effectively handled by dropping the finest wavelet scale. This step is called multiple component transformation in the JPEG 2000 language since its usage is not restricted to the RGB color model.
Tiling After color transformation, the image is split into so-called tiles, rectangular regions of the image that are transformed and encoded separately. Tiles can be any size, and it is also possible to consider the whole image as one single tile. Once the size is chosen, all the tiles will have the same size (except optionally those on the right and bottom borders). Dividing the image into tiles is advantageous in that the decoder will need less memory to decode the image and it can opt to decode only selected tiles to achieve a partial decoding of the image. The disadvantage of this approach is that the quality of the picture decreases due to a lower peak signal-to-noise ratio. Using many tiles can create a blocking effect similar to the older JPEG 1992 standard.
Wavelet transform
These tiles are then wavelet-transformed to an arbitrary depth, in contrast to JPEG 1992 which uses an 8×8 block-size discrete cosine transform. JPEG 2000 uses two different wavelet transforms: