awaforge

pdfText

AGPL-3.0-onlyRelease 2L4

Text state + Tm/Tlm matrices + Unicode extraction — ISO 32000-2 §9.3 / §9.4.

Module pdfText | Source packages/front/office/pdf/src/content/text.js | Deps pdfErrors | Worker-safe yes

Applies the operators that mutate gstate.text (Tf, BT, Td, TD, Tm, T*) and exposes extractText, which decodes a Tj/TJ/'/" operand into Unicode through a caller-supplied cidToUnicode function (typically built from @awacloud/fonts' cmapToUnicode module, @awacloud/fonts/cmap-to-unicode). ToUnicode resolution is deliberately not done here, so the module stays worker-safe with no font dependency.

Resolve

const t = runtime.resolve('pdfText');
// Returns: { setFont, beginTextObject, td, tdSetLeading,
//            setTextMatrix, nextLine, rawStringBytes, extractText }

API

Method Signature Returns
setFont (gstate, fontResource: string, size: number) => void Applies Tf.
beginTextObject () => { Tm, Tlm } Initialises BT — both matrices identity.
td (state, tx, ty) => void Operator Td.
tdSetLeading (gstate, state, tx, ty) => void Operator TD — also sets gstate.text.leading = -ty.
setTextMatrix (state, m: number[6]) => void Operator Tm.
nextLine (gstate, state) => void Operator T*.
rawStringBytes (stringObj) => Uint8Array Raw bytes of a typed string operand.
extractText (op, font, cidToUnicode) => string Decodes Tj/TJ/'/".

state is the { Tm, Tlm } record returned by beginTextObject; gstate is a graphics state from pdfGraphics, whose text sub-object is mutated in place.

extractText

  • Single-byte fonts (font.subtype !== 'Type0'): each byte is a CID.
  • CID fonts (font.subtype === 'Type0'): big-endian byte pairs.
  • Numbers inside a TJ array (positioning adjustments) contribute no text.
  • The " operator reads its string from args[2]; Tj and ' from args[0].
  • A glyph with no ToUnicode mapping yields the replacement character '�'.

Examples

Minimal extraction pipeline

const t = runtime.resolve('pdfText');
const state = t.beginTextObject();
let acc = '';
for (const op of ops) {
    if (op.op === 'Tf')      t.setFont(gstate, op.args[0].value, op.args[1].value);
    else if (op.op === 'Td') t.td(state, op.args[0].value, op.args[1].value);
    else if (op.op === 'Tj' || op.op === 'TJ') {
        acc += t.extractText(op, currentFont, cidToUnicode);
    }
}

Set the text matrix

t.setTextMatrix(state, [1, 0, 0, 1, 72, 720]);  // (72, 720) in user space

Raw bytes for an external ToUnicode

const raw = t.rawStringBytes(op.args[0]);  // Uint8Array
const text = customCmap.decode(raw);

Errors

Code Class When
pdf/text/bad-matrix ContractError Tm matrix is not 6 elements.
pdf/text/bad-string ContractError rawStringBytes given something other than a {type:'string'}.

See also