JPEG XT

JPEG XT is a backward-compatible extension of the JPEG graphics format. It offers higher bit depths, high dynamic range, lossless and near-lossless compression, and transparency.

JPEG XT is similar in concept to JPEG-HDR. Its precise relationship to JPEG-HDR is not clear; the formats do not appear to be compatible.

All the critical parts of the standard were published as of 2016-10-15. The final part of the original standard was published in 2018-03.

Format details
Like JPEG-HDR, it uses APP11 segments. Unlike JPEG-HDR, the data in those segments uses boxes/atoms format, with the brand " ".

Identification
A JPEG XT file contains one or more APP11 segments (see JPEG) whose data begins with ASCII "". Note that the signature is just these two bytes, and has no NUL terminator.

Specifications
Most of these documents are not free to download.
 * ISO/IEC 18477-1:2015 - Part 1: Scalable compression and coding of continuous-tone still images
 * ISO/IEC 18477-1 preview
 * ISO/IEC 18477-2:2016 - Part 2: Extensions for high dynamic range images
 * ISO/IEC 18477-3:2015 - Part 3: Box file format
 * ISO/IEC 18477-4:2017 - Part 4: Conformance testing
 * ISO/IEC 18477-5:2018 - Part 5: Reference software
 * ISO/IEC 18477-6:2016 - Part 6: IDR Integer Coding
 * ISO/IEC 18477-7:2016 - Part 7: HDR Floating-Point Coding
 * ISO/IEC 18477-8:2016 - Part 8: Lossless and Near-lossless Coding
 * ISO/IEC 18477-9:2016 - Part 9: Alpha Channel Coding

Software

 * Software for JPEG XT
 * Thomas Richter's libjpeg

Links

 * Overview of JPEG XT