Lossless JPEG (original)


 * 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