Save XMP metadata in canonical format for PDF/A documents.

DEVSIX-6355

Author: dmitry.radchuk

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfDocument.java

@@ -173,6 +173,8 @@ public class PdfDocument implements IEventDispatcher, Closeable {
     final PdfXrefTable xref = new PdfXrefTable();
     protected FingerPrint fingerPrint;
 
+    protected SerializeOptions serializeOptions = new SerializeOptions();
+
     protected final StampingProperties properties;
 
     protected PdfStructTreeRoot structTreeRoot;
@@ -334,6 +336,7 @@ protected void setXmpMetadata(byte[] xmpMetadata) {
      * @throws XMPException on serialization errors
      */
     public void setXmpMetadata(XMPMeta xmpMeta, SerializeOptions serializeOptions) throws XMPException {
+        this.serializeOptions = serializeOptions;
         setXmpMetadata(XMPMetaFactory.serializeToBuffer(xmpMeta, serializeOptions));
     }
 
@@ -345,7 +348,6 @@ public void setXmpMetadata(XMPMeta xmpMeta, SerializeOptions serializeOptions) t
      * @throws XMPException on serialization errors
      */
     public void setXmpMetadata(XMPMeta xmpMeta) throws XMPException {
-        SerializeOptions serializeOptions = new SerializeOptions();
         serializeOptions.setPadding(2000);
         setXmpMetadata(xmpMeta, serializeOptions);
     }
@@ -1869,6 +1871,24 @@ public SequenceId getDocumentIdWrapper() {
         return documentId;
     }
 
+    /**
+     * Sets a persistent XMP metadata serialization options.
+     *
+     * @param serializeOptions serialize options
+     */
+    public void setSerializeOptions(SerializeOptions serializeOptions) {
+        this.serializeOptions = serializeOptions;
+    }
+
+    /**
+     * Gets a persistent XMP metadata serialization options.
+     *
+     * @return serialize options
+     */
+    public SerializeOptions getSerializeOptions() {
+        return this.serializeOptions;
+    }
+
     /**
      * Gets list of indirect references.
      *

kernel/src/main/java/com/itextpdf/kernel/xmp/impl/XMPSerializerRDF.java

@@ -909,7 +909,9 @@ private void declareNamespace(String prefix, String namespace, Set<String> usedP
 				return;
 			}
 		}
-
+		if (prefix.isEmpty()) {
+			return;
+		}
 		if (!usedPrefixes.contains(prefix))
 		{
 			writeNewline();

kernel/src/test/java/com/itextpdf/kernel/pdf/PdfDocumentTest.java

@@ -58,6 +58,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.kernel.pdf.xobject.PdfFormXObject;
 import com.itextpdf.kernel.pdf.xobject.PdfImageXObject;
 import com.itextpdf.kernel.utils.CompareTool;
+import com.itextpdf.kernel.xmp.options.SerializeOptions;
 import com.itextpdf.test.ExtendedITextTest;
 import com.itextpdf.test.LogLevelConstants;
 import com.itextpdf.test.annotations.LogMessage;
@@ -606,6 +607,14 @@ public void rootCannotBeReferenceFromTrailerTest() throws IOException {
         Assert.assertEquals(KernelExceptionMessageConstant.CORRUPTED_ROOT_ENTRY_IN_TRAILER, e.getMessage());
     }
 
+    @Test
+    public void setSerializeOptionsTest() {
+        PdfDocument document = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+        SerializeOptions options = new SerializeOptions().setUseCanonicalFormat(true);
+        document.setSerializeOptions(options);
+        Assert.assertEquals(options, document.getSerializeOptions());
+    }
+
     private static class IgnoreTagStructurePdfDocument extends PdfDocument {
 
         IgnoreTagStructurePdfDocument(PdfReader reader) {

pdfa/src/test/java/com/itextpdf/pdfa/PdfAXmpTest.java

@@ -43,9 +43,17 @@ This file is part of the iText (R) project.
 package com.itextpdf.pdfa;
 
 import com.itextpdf.kernel.pdf.PdfAConformanceLevel;
+import com.itextpdf.kernel.pdf.PdfDocument;
 import com.itextpdf.kernel.pdf.PdfOutputIntent;
+import com.itextpdf.kernel.pdf.PdfReader;
 import com.itextpdf.kernel.pdf.PdfWriter;
 import com.itextpdf.kernel.utils.CompareTool;
+import com.itextpdf.kernel.xmp.XMPConst;
+import com.itextpdf.kernel.xmp.XMPException;
+import com.itextpdf.kernel.xmp.XMPMeta;
+import com.itextpdf.kernel.xmp.XMPMetaFactory;
+import com.itextpdf.kernel.xmp.options.PropertyOptions;
+import com.itextpdf.kernel.xmp.options.SerializeOptions;
 import com.itextpdf.test.ExtendedITextTest;
 import com.itextpdf.test.annotations.type.IntegrationTest;
 import java.io.FileInputStream;
@@ -108,4 +116,45 @@ public void keywordsInfoTestPdfA2b() throws IOException, InterruptedException {
         Assert.assertNull(ct.compareXmp(outFile, cmpFile, true));
     }
 
+    @Test
+    public void saveAndReadDocumentWithCanonicalXmpMetadata() throws IOException, XMPException {
+        String outFile = destinationFolder + "saveAndReadDocumentWithCanonicalXmpMetadata.pdf";
+        String cmpFile = cmpFolder + "cmp_saveAndReadDocumentWithCanonicalXmpMetadata.pdf";
+        PdfAConformanceLevel conformanceLevel = PdfAConformanceLevel.PDF_A_2B;
+        PdfOutputIntent outputIntent;
+
+        try (InputStream is = new FileInputStream(sourceFolder + "sRGB Color Space Profile.icm")) {
+            outputIntent = new PdfOutputIntent("Custom", "", "http://www.color.org", "sRGB IEC61966-2.1", is);
+        }
+
+        try (PdfADocument doc = new PdfADocument(new PdfWriter(outFile), conformanceLevel, outputIntent)) {
+            doc.addNewPage();
+            XMPMeta xmp = XMPMetaFactory.create();
+            xmp.setProperty(XMPConst.NS_PDFA_ID, XMPConst.PART, conformanceLevel.getPart(), new PropertyOptions().setSchemaNode(true));
+            xmp.setProperty(XMPConst.NS_PDFA_ID, XMPConst.CONFORMANCE, conformanceLevel.getConformance(), new PropertyOptions().setSchemaNode(true));
+            SerializeOptions options = new SerializeOptions().setUseCanonicalFormat(true).setUseCompactFormat(false);
+            doc.setXmpMetadata(xmp, options);
+            doc.setTagged();
+        }
+        // Closing document and reopening it to flush it XMP metadata ModifyDate
+        try (PdfDocument doc = new PdfDocument(new PdfReader(outFile));
+             PdfDocument cmpDoc = new PdfDocument(new PdfReader(cmpFile))) {
+            byte[] rdf = doc.getXmpMetadata();
+            byte[] expectedRdf = cmpDoc.getXmpMetadata();
+            // Comparing angle brackets, since it's the main difference between canonical and compact format.
+            Assert.assertEquals(count(expectedRdf, (byte)'<'), count(rdf, (byte)'<'));
+            Assert.assertNull(new CompareTool().compareXmp(cmpFile, outFile, true));
+        }
+    }
+
+    private int count(byte[] array, byte b) {
+        int counter = 0;
+        for (byte each : array) {
+            if (each == b) {
+                counter++;
+            }
+        }
+        return counter;
+    }
+
 }