Lossless JPEG (original)

File Format
Name	Lossless JPEG (original)
Ontology	Electronic File Formats Graphics Lossless JPEG (original)
Extension(s)	.jpg, .ljpg, .ljpeg
LoCFDD	fdd000334
Released	1992

See Lossless JPEG for other uses of the term.

The original lossless JPEG (sometimes called lossless JPEG-1) refers to the original JPEG format when used with lossless compression, instead of the usual lossy compression. It is a standard type of JPEG file, defined in the original JPEG standard (ITU-T Rec. T.81). Though few applications support it, it has found some use in the medical industry (see DICOM), and in some raw camera formats. Note that this format is distinct from JPEG-LS.

A lossless JPEG image may have any bit depth from 2 to 16 bits per sample. The compression scheme uses Huffman coding or arithmetic coding.

Identification

A lossless JPEG file is identified by the presence of an SOF3, SOF7, SOF11, or SOF15 segment. Refer to JPEG for a discussion of JPEG segments.

Specifications

• ITU-T Rec. T.81: The JPEG standard

Software

• Thomas Richter's libjpeg
• ljpeg-6b.tar.gz: Lossless JPEG patch for IJG libjpeg 6b (presumably by Ken Murchison)
• Lossless JPEG Codec (Cornell University): pnmtoljpg, ljpgtopnm
• Stanford PVRG JPEG
  • Linux port by Matteo Roffilli
• dcraw includes a (probably incomplete) Lossless JPEG decoder

Sample files

• ljpeg-6b.tar.gz → testimgl.jpg
• ljpg.tar.Z → F-18.ljpg