Overview
ISO 12639:2004/Amd 1:2007 is an amendment to the TIFF/IT prepress exchange standard that defines how JBIG2-Amd2 compressed codestreams are incorporated into TIFF/IT image files. The amendment enables the use of JBIG2-Amd2 for TIFF/IT-BP (binary picture) and TIFF/IT-SD (screened data), delivering efficient, lossless bi-level compression suited to halftone and binary printing data.
Key Topics
- Scope of use: JBIG2-Amd2 compression is permitted only for TIFF/IT-BP and TIFF/IT-SD image types. It is explicitly disallowed for TIFF/IT-BP/P1, -BP/P2, -SD/P1, -SD/P2 and for TIFF/IT-CT, -LW, -HC, -MP and -BL.
- Compression tag value: A TIFF/IT image using JBIG2-Amd2 shall set the Compression field to 34715 (SHORT = 34715).
- Strip tag requirements:
- TIFF/IT-BP files: counts of StripOffsets and StripByteCounts shall be 1.
- TIFF/IT-SD files: SamplesPerPixel value and counts of StripOffsets and StripByteCounts shall be 4 (one strip per colour separation, each containing a JBIG2 codestream).
- Codestream structure: The JBIG2-Amd2 codestream for TIFF/IT-BP follows a constrained segment sequence: a profiles segment, a page-information segment, at least two immediate-lossless-generic-region segments, and an end-of-page segment. The annex references profile 0x00000008 for the strip format.
- Alignment and page fields: Page-bitmap width must be the smallest multiple of 8 that is ≥ ImageWidth (byte-aligned lines). Page-bitmap-height is specified relative to ImageLength (the annex requires page-bitmap-height > ImageLength by 1 in the page-info segment).
Applications
- Prepress workflows: Use JBIG2-Amd2 in TIFF/IT to compress bi-level halftone separations for reduced file sizes while preserving lossless fidelity important in printing and reprographics.
- Interoperability: Standardized tag values and strip formats improve reliable data exchange between raster image processors (RIPs), pagesetters and service providers.
- Archiving and transfer: Effective compression of binary imagery lowers storage and bandwidth costs for large print-ready files without changing TIFF/IT image semantics.
Related Standards
- ISO/IEC 14492:2001 and ISO/IEC 14492:2001/Amd.2:2003 (JBIG2 and JBIG2-Amd2) - specifies the JBIG2 codestreams used by this amendment.
- ISO 12639:2004 (base TIFF/IT standard) - amendment integrates JBIG2-Amd2 into existing TIFF/IT tag and strip conventions.
- ISO/IEC 11544 - prior bi-level image coding context referenced in the bibliography.
This amendment focuses on practical interoperability: defined tag values, strip counts and a constrained JBIG2 codestream layout enable implementers to add JBIG2-Amd2 compression to TIFF/IT encoders and decoders while maintaining compatibility with prepress workflows.
Open preview (PDF)Graphic technology — Prepress digital data exchange — Tag image file format for image technology (TIFF/IT) — Amendment 1: Use of JBIG2-Amd2 compression in TIFF/IT
