F.2 Encapsulated JPEG-LS Encoded Images

The International Standards Organization (ISO/IEC JTC1/SC2/WG10) has prepared an International Standard, ISO/IS-14495-1 (JPEG-LS Part 1), for the digital compression and coding of continuous-tone still images. This standard is known as the JPEG-LS Standard.

Part 1 of the JPEG-LS Standard sets out requirements and implementation guidelines for the coded representation of compressed image data to be interchanged between applications. The processes and representations are intended to be generic in order to support the broad range of applications for color and grayscale still images for the purpose of communications and storage within computer systems.

The JPEG-LS Standard specifies a single lossy (near-lossless) code process that can achieve lossless compression by constraining the absolute error value during encoding to zero. The lossless and lossy (near-lossless) coding is based on a predictive scheme with statistical modeling, in which differences between pixels and their surround are computed and their context modeled prior to coding, with a run-length escape mechanism. This scheme achieves consistently better compression in lossless mode than the lossless processes of JPEG defined in ISO 10918-1, with less complexity.

Though a different coding process from those specified in ISO 10918-1 is used, the syntax of the encoded bit stream is closely related.

A single JPEG-LS process is used for bit depths up to 16 bits.

Inclusion of a JPEG-LS coded image in a DICOM message is facilitated by the use of specific Transfer Syntaxes that are defined in Annex A.