XMP metadata

PDF 2.0 and ISO 19445 XMP metadata for image and document proofing

Peter Wyatt // January 24, 2023

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This article provides recommendations to industry as to how ISO 19445 might be used with PDF 2.0 and related technology updates relevant to the graphic arts industry.

ISO 19445 Graphic technology — Metadata for graphic arts workflow — XMP metadata for image and document proofing is a metadata standard for PDF technology developed by ISO TC 130 WG 2 that “specifies the set of metadata to be used to communicate the approval status, proof preparation and viewing parameters for images and documents that are used in the graphic arts print production workflow.”.

Like all ISO publications, ISO 19445 is systematically reviewed by its ISO committee every 5 years to ensure its relevance and correctness. As a result of the 2021 review, a new 2022 dated revision was recently published updating wording, layout and structure in order to conform to the latest ISO “house style rules”, but unfortunately, some technical changes to support PDF 2.0 and PDF/X-6 were not accepted in time.

Referencing PDF 2.0

The XMP metadata defined by ISO 19445 is equally applicable to all versions of PDF. However, ISO 19445:2022 only refers to PDF 1.7 via an undated normative reference to ISO 32000-1, whereas it should also refer to PDF 2.0 via an undated reference to ISO 32000-2, as in reality, ISO 19445 is equally applicable to PDF 2.0-based PDF/X-6 (ISO 15930-9:2020) files as well as earlier PDF 1.x-based PDF/X files.

Undated references

All normative references in ISO 19445 are undated, meaning that the latest edition and all amendments of each referenced document are included in the reference. This makes sense, since ISO 19445 is only defining XMP metadata that is used in conjunction with PDF data:

  • For PDF 2.0 (ISO 32000-2), this should reference the latest 2020 edition as well as the forthcoming Amendment 1 with additional errata corrections;
  • For ICC.1 profiles (ISO 15076), this would include the forthcoming ISO equivalent to support ICC.1 v4.4.0.0 (already available from the International Color Consortium website).

PDF 2.0 black point compensation

Table 1 in ISO 19445 defines all properties of an ImageApprovals record. The BlackPointCompensation Boolean property is defined appropriately for PDF 1.x files, but its definition needs to be slightly refined for PDF 2.0. This is because PDF 2.0 introduced Black Point Compensation (BPC) control via the new UseBlackPtComp entry in graphics state parameter dictionaries (see ISO 32000-2:2020, Table 57 — Entries in a graphics state parameter dictionary), thereby allowing PDF 2.0 files to control their own BPC behavior on an object-by-object basis. Accordingly, the ISO 19445 BlackPointCompensation Boolean property for PDF 2.0 files would be the BPC setting used only when UseBlackPtComp has the value Default.

PDF 2.0 digital signatures

In section 5.2 Using digital signatures, the reference to ISO 32000-1 (PDF 1.7) should also include a reference to PDF 2.0 (ISO 32000-2) to indicate support for PDF 2.0-based digital signatures.

Conclusion

As can be seen by this very short list, ISO 19445 is easily applicable to PDF 2.0 and thus PDF/X-6, as well as updates to ICC.1 color profiles. Maybe the only remaining significant technical discussion topics are if (or how) iccMAX color profiles (ICC.2 ISO 20677) or CxF/X-4 data in PDF 2.0 (see the SpectralData entry in ISO 32000-2:2020, Table 401 — Entries in an output intent dictionary) might be used for image and document proofing. Currently ISO TC 130 WG 2 believes these topics are not sufficiently used in industry for standardization. However if this work is important for you, please reach out to the PDF Association or your national standards body.


ABOUT THE AUTHORS

Peter Wyatt
Peter Wyatt

Peter Wyatt is the PDF Association’s CTO and an independent technology consultant with deep file format and parsing expertise, who is a developer and researcher actively working on PDF technologies for more than 20 years. He is Project co-Leader of ISO 32000 (the core PDF standard), co-Chairs the PDF Association PDF TWG and is the PDF Association’s Principal Scientist leading …

ABOUT THE AUTHORS

Peter Wyatt

Peter Wyatt

Peter Wyatt is the PDF Association’s CTO and an independent technology consultant with deep file format and parsing expertise, who …