Question

我需要读取和写入PDF / A文件的XMP元数据。

我正在使用itextsharp 7并尝试了几种方法来实现我的目标，但没有取得多大成功。像control:Anzahl_Zeichen_Titel这样的字段是我的目标。下面的代码应该做的工作，但我无法弄清楚究竟是怎么做的。

PdfADocument pdfADocument = new PdfADocument(new PdfReader(Vorlage), new PdfWriter(Ausgabe), new StampingProperties());
XMPMeta xmpMeta = XMPMetaFactory.ParseFromBuffer(pdfADocument.GetXmpMetadata());
XMPProperty test1 = xmpMeta.GetProperty("ftx:ControlData", "control:Anzahl_Zeichen_Vorname");
XMPProperty test2 = xmpMeta.GetProperty("http://www.aiim.org/pdfa/ns/schema#", "ControlData");

当我使用test1版本时，它向我显示了一个XMPException“Unregistered schema namespace URI”。第二个似乎有效，但test2变量为null。

<?xpacket begin="ï»¿" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.6-c015 84.159810, 2016/09/10-02:41:30        ">
   <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
      <rdf:Description rdf:about=""
            xmlns:xmp="http://ns.adobe.com/xap/1.0/"
            xmlns:dc="http://purl.org/dc/elements/1.1/"
            xmlns:pdf="http://ns.adobe.com/pdf/1.3/"
            xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
            xmlns:stEvt="http://ns.adobe.com/xap/1.0/sType/ResourceEvent#"
            xmlns:pdfaExtension="http://www.aiim.org/pdfa/ns/extension/"
            xmlns:pdfaSchema="http://www.aiim.org/pdfa/ns/schema#"
            xmlns:pdfaProperty="http://www.aiim.org/pdfa/ns/property#"
            xmlns:pdfaType="http://www.aiim.org/pdfa/ns/type#"
            xmlns:pdfaField="http://www.aiim.org/pdfa/ns/field#"
            xmlns:ftx="http://ns.ftx.com/forms/1.0/"
            xmlns:control="http://ns.ftx.com/forms/1.0/controldata/">
         <xmp:CreatorTool>QuarkXPress(R) 8.12</xmp:CreatorTool>
         <xmp:CreateDate>2017-03-14T08:56:49+01:00</xmp:CreateDate>
         <xmp:ModifyDate>2017-04-11T14:35:21+02:00</xmp:ModifyDate>
         <xmp:MetadataDate>2017-04-11T14:35:21+02:00</xmp:MetadataDate>
         <dc:format>application/pdf</dc:format>
         <!-- snip -->
         <ftx:ControlData rdf:parseType="Resource">
            <control:Anzahl_Zeichen_Titel>0</control:Anzahl_Zeichen_Titel>
            <control:Anzahl_Zeichen_Vorname>0</control:Anzahl_Zeichen_Vorname>
            <control:Anzahl_Zeichen_Namenszusatz>0</control:Anzahl_Zeichen_Namenszusatz>
            <control:Anzahl_Zeichen_Hausnummer>0</control:Anzahl_Zeichen_Hausnummer>
            <control:Anzahl_Zeichen_Postleitzahl>0</control:Anzahl_Zeichen_Postleitzahl>
            <control:Anzahl_Zeichen_Wohnsitzlaendercode>0</control:Anzahl_Zeichen_Wohnsitzlaendercode>
            <control:Auftragsnummer_Einsender>0</control:Auftragsnummer_Einsender>
            <control:Formularnummer>10</control:Formularnummer>
            <control:Formularversion>07.2017</control:Formularversion>
         </ftx:ControlData>
      </rdf:Description>
   </rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>

我如何使用这些方法创建和读取有效数据？

Answer 1

XMPMeta.getProperty记录为：

/**
 * The property value getter-methods all take a property specification: the first two parameters
 * are always the top level namespace URI (the &quot;schema&quot; namespace) and the basic name
 * of the property being referenced. See the introductory discussion of path expression usage
 * for more information.
 * <p>
 * All of the functions return an object inherited from <code>PropertyBase</code> or
 * <code>null</code> if the property does not exists. The result object contains the value of
 * the property and option flags describing the property. Arrays and the non-leaf levels of
 * nodes do not have values.
 * <p>
 * See {@link PropertyOptions} for detailed information about the options.
 * <p>
 * This is the simplest property getter, mainly for top level simple properties or after using
 * the path composition functions in XMPPathFactory.
 * 
 * @param schemaNS The namespace URI for the property. May be <code>null</code> or the empty
 *        string if the first component of the propName path contains a namespace prefix. The
 *        URI must be for a registered namespace.
 * @param propName The name of the property. May be a general path expression, must not be
 *        <code>null</code> or the empty string. Using a namespace prefix on the first
 *        component is optional. If present without a schemaNS value then the prefix specifies
 *        the namespace. The prefix must be for a registered namespace. If both a schemaNS URI
 *        and propName prefix are present, they must be corresponding parts of a registered
 *        namespace.
 * @return Returns a <code>XMPProperty</code> containing the value and the options or
 *         <code>null</code> if the property does not exist.
 * @throws XMPException Wraps all errors and exceptions that may occur.
 */
XMPProperty getProperty(String schemaNS, String propName) throws XMPException;

特别是第一个参数必须是名称空间URI ，所以

XMPProperty test1 = xmpMeta.GetProperty("ftx:ControlData", "control:Anzahl_Zeichen_Vorname");

显然是错的。

你的第二个选择

XMPProperty test2 = xmpMeta.GetProperty("http://www.aiim.org/pdfa/ns/schema#", "ControlData");

正确地将名称空间URI 作为第一个参数。不幸的是，它不是http://ns.ftx.com/forms/1.0/所讨论的属性的名称空间URI。

因此，您应该尝试

XMPProperty test2 = xmpMeta.GetProperty("http://ns.ftx.com/forms/1.0/", "ControlData");

或（因为记录的的schemaNS可能是null，或者如果propName路径的第一个组件包含名称空间前缀，则为空字符串。

XMPProperty test2 = xmpMeta.GetProperty(null, "ftx:ControlData");

Answer 2

在mkl的回答的帮助下，我找到了如何读取和写入所需的数据。

private const string NsControlData = "http://ns.ftx.com/forms/1.0/";
private const string NsControl = "http://ns.ftx.com/forms/1.0/controldata/";

// Opens the template file as PDF/A document.
PdfADocument pdfADocument = new PdfADocument(new iText.Kernel.Pdf.PdfReader("input.pdf"), new PdfWriter("output.pdf"), new StampingProperties());

// Reading the metadata from input file.
byte[] xmpMetadata = pdfADocument.GetXmpMetadata(); 

// Parse the metadata
XMPMeta parser = XMPMetaParser.Parse(xmpMetadata, new ParseOptions());

// Read a value
XMPProperty anzahlZeichenTitel = parser.GetStructField(NsControlData, "ControlData", NsControl, "Anzahl_Zeichen_Titel");
// Write a value
parser.SetStructField(NsControlData, "ControlData", NsControl, "Anzahl_Zeichen_Titel", "333");

// writing new file with new metadata.
pdfADocument.SetXmpMetadata(parser);
pdfADocument.GetWriter().Flush();
pdfADocument.Close();

在PDF / A文档中读取和编写xml元数据

2 个答案: