Lossless JPEG (original)
From Just Solve the File Format Problem
- 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.
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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
- dcraw includes a (probably incomplete) Lossless JPEG decoder
Sample files
- ljpeg-6b.tar.gz → testimgl.jpg
- ljpg.tar.Z → F-18.ljpg
