Function flattenPdf

apps/OpenSign/src/constant/Utils.js:3731–3788

(pdfFile)

 * @returns {Promise<Uint8Array>} flatPdf - PDF file in Uint8Array
 */
export const flattenPdf = async (pdfFile) => {
  const pdfDoc = await PDFDocument.load(pdfFile, { ignoreEncryption: true });

  let form;
  try {
    form = pdfDoc.getForm();
  } catch {
    // No form, nothing to flatten
    return await pdfDoc.save({ useObjectStreams: false });
  }

  const pages = pdfDoc.getPages();

  const helvetica = await pdfDoc.embedFont(StandardFonts.Helvetica);
  const helveticaBold = await pdfDoc.embedFont(StandardFonts.HelveticaBold);
  const zapf = await pdfDoc.embedFont(StandardFonts.ZapfDingbats);

  const fields = form.getFields();

  for (const field of fields) {
    const type = field.constructor.name;

    if (type === "PDFSignature") {
      continue;
    }

    const widgets = _safeGetWidgets(field);

    for (const widget of widgets) {
      const rect = _getWidgetRect(widget, pdfDoc);
      const page = _getWidgetPage(pdfDoc, pages, widget);

      if (!rect || !page) continue;

      _drawWidgetBox(page, rect);

      if (type === "PDFTextField") {
        _drawTextField(page, field, rect, helvetica);
      } else if (type === "PDFCheckBox") {
        _drawCheckBox(page, field, rect, zapf);
      } else if (type === "PDFRadioGroup") {
        _drawRadioGroup(page, field, widget, rect);
      } else if (type === "PDFDropdown") {
        _drawDropdown(page, field, rect, helvetica);
      } else if (type === "PDFOptionList") {
        _drawOptionList(page, field, rect, helvetica);
      } else if (type === "PDFButton") {
        // Push buttons are interactive controls, not meaningful data fields.
      }
    }
  }

  if (fields.length > 0) {
    _removeWidgetAnnotations(pdfDoc);
  }

  return await pdfDoc.save({ useObjectStreams: false });
};