awaforge

pdfResources

AGPL-3.0-onlyRelease 2L4

Resolution of a Page's or Form XObject's /Resources dictionary — ISO 32000-2 §7.8.3.

Module pdfResources | Source packages/front/office/pdf/src/document/resources.js | Deps pdfErrors, pdfParser | Worker-safe yes

Six named sub-dictionaries map the local names used inside a content stream to indirect objects: /Font, /XObject, /ColorSpace, /ExtGState, /Pattern, /Shading. A legacy /ProcSet is read but never required (deprecated in PDF 2.0). Resources are inheritable: a Page without its own /Resources walks up the page tree's /Parent chain (§7.7.3.4). resolvePageResources implements that walk with a cycle guard.

Any category value may itself be an indirect reference (§7.3.10). Real documents do this: a measured ANSSI guide carries /ExtGState as N 0 R on 56 of its 58 pages. Rejecting that used to throw away the page's whole resource map, fonts included. The resolver you pass reaches objects inside object streams, because it is the document's own _raw.resolve.

Resolve

const r = runtime.resolve('pdfResources');
// Returns: { typeResources, resolvePageResources, lookupResource }

API

Method Signature Returns
typeResources (dict|null, resolveRef?) => Resources Direct typing. With resolveRef, an indirect category (/Font 12 0 R) is resolved through it; a category that resolves to null is treated as absent.
resolvePageResources (pageDict, resolveRef) => Resources Inherited walk, at most 64 levels; passes resolveRef on to typeResources.
lookupResource (resources, category, name, resolveRef?) => object Named lookup.

Resources shape

{
    Font:       { [name]: PdfObject },
    XObject:    { [name]: PdfObject },
    ColorSpace: { [name]: PdfObject },
    ExtGState:  { [name]: PdfObject },
    Pattern:    { [name]: PdfObject },
    Shading:    { [name]: PdfObject },
    ProcSet:    string[] | null,
    raw:        object | null
}

lookupResource returns the resolved object directly (ref → object) when resolveRef is supplied, otherwise the typed entry (possibly a ref).

Examples

Page → Resources

const r = runtime.resolve('pdfResources');
const res = r.resolvePageResources(pageDict, doc._raw.resolve);
res.Font;       // { F1: <typed font dict>, F2: … }
res.ExtGState;  // { GS1: … }

Look up a named font

const fontDict = r.lookupResource(res, 'Font', 'F1', doc._raw.resolve);
const typed = runtime.resolve('pdfFont').typeFont(fontDict);

Direct typing without the walk

const res = r.typeResources(pageDict.entries.Resources);

Errors

Code Class When
pdf/resources/not-dict ParseError /Resources is not a dictionary.
pdf/resources/bad-subdict ParseError A sub-dictionary (/Font, …) is not a dictionary — or it is an indirect reference and no resolveRef was supplied.
pdf/resources/bad-shape ParseError /Resources is neither a dictionary nor a reference.
pdf/resources/cycle ParseError Cycle detected in the /Parent chain.
pdf/resources/unknown-category ParseError Invalid category passed to lookupResource.
pdf/resources/missing-name ParseError Name not found in the category.

See also