Add PDF/UA subset (foliojs#1485)

* Added PDF/UA subset and its metadata

* Added PDF/UA metadata unit tests

* Added PDF/UA subset to accessibility docs

* Updated change log for PDF/UA subset

Author: andreiaugustin

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## pdfkit changelog
 
+### Unreleased
+
+- Add subset for PDF/UA
+
 ### [v0.14.0] - 2023-11-09
 
 - Add support for PDF/A-1b, PDF/A-1a, PDF/A-2b, PDF/A-2a, PDF/A-3b, PDF/A-3a

docs/accessibility.md

@@ -14,6 +14,8 @@ Universal Accessibility) document (which is an extension of Tagged PDF):
  * Pass the option `pdfVersion: '1.5'` (or a higher version) when creating your `PDFDocument`
    (depending on the features you use, you may only need 1.4; refer to the PDF reference for
    details).
+ * Pass the option `subset: 'PDF/UA'` when creating your `PDFDocument` (if you wish the PDF to
+   be identified as PDF/UA-1).
  * Pass the option `tagged: true` when creating your `PDFDocument` (technically, this sets the
    `Marked` property in the `Markings` dictionary to `true` in the PDF).
  * Provide a `Title` in the `info` option, and pass `displayTitle: true` when creating your

lib/mixins/pdfua.js

@@ -0,0 +1,24 @@
+
+export default {
+
+    initPDFUA() {
+        this.subset = 1;
+    },
+
+    endSubset() {
+        this._addPdfuaMetadata();
+    },
+
+    _addPdfuaMetadata() {
+        this.appendXML(this._getPdfuaid());
+    },
+
+    _getPdfuaid() {
+        return `
+        <rdf:Description xmlns:pdfuaid="http://www.aiim.org/pdfua/ns/id/" rdf:about="">
+            <pdfuaid:part>${this.subset}</pdfuaid:part>
+        </rdf:Description>
+        `;
+    },
+
+}

lib/mixins/subsets.js

@@ -1,4 +1,5 @@
 import PDFA from './pdfa';
+import PDFUA from './pdfua';
 
 export default {
     _importSubset(subset) {
@@ -20,6 +21,10 @@ export default {
                 this._importSubset(PDFA);
                 this.initPDFA(options.subset);
                 break;
+            case 'PDF/UA':
+                this._importSubset(PDFUA);
+                this.initPDFUA();
+                break;
         }
     }
 }

tests/unit/pdfua.spec.js

@@ -0,0 +1,37 @@
+import PDFDocument from '../../lib/document';
+import { logData } from './helpers';
+
+describe('PDF/UA', () => {
+
+    test('metadata is present', () => {
+        let options = {
+            autoFirstPage: false,
+            pdfVersion: '1.7',
+            subset: 'PDF/UA',
+            tagged: true
+        };
+        let doc = new PDFDocument(options);
+        const data = logData(doc);
+        doc.end();
+        expect(data).toContainChunk([
+            `11 0 obj`,
+            `<<\n/length 841\n/Type /Metadata\n/Subtype /XML\n/Length 843\n>>`
+        ]);
+    });
+
+    test('metadata constains pdfuaid part', () => {
+        let options = {
+            autoFirstPage: false,
+            pdfVersion: '1.7',
+            subset: 'PDF/UA',
+            tagged: true
+        };
+        let doc = new PDFDocument(options);
+        const data = logData(doc);
+        doc.end();
+        let metadata = Buffer.from(data[24]).toString();
+
+        expect(metadata).toContain('pdfuaid:part>1');
+    });
+
+});