Not only shouldn't you compress the data in the XMP, but the spec
actually considered it "verbotten". In addition, there are some
tools out there that will crash if fed compressed XMP.
Leonard
On Apr 9, 2008, at 12:14 PM, Bruno Lowagie wrote:
> Ning Zhao wrote:
>> P.S.: Just bought the book "iText in action" and reading Chapter 18.
>
> I thought of replacing the XMP stream at the lower level too:
> with PRStream.setData(). The problem you'll experience is that
> setData() compresses the stream by default. That's typically not
> what you want to happen with an XMP stream. I've adapted the
> example I've sent before to work around this problem (look at
> the lines where I change the value of Document.compress). That's
> not a very elegant solution. Maybe I'll provide an extra setData
> method that takes a boolean to let the developer decide whether
> or not the data has to be compressed.
> best regards,
> Bruno
> import java.io.ByteArrayOutputStream;
> import java.io.FileOutputStream;
> import java.io.IOException;
>
> import com.lowagie.text.Document;
> import com.lowagie.text.DocumentException;
> import com.lowagie.text.Paragraph;
> import com.lowagie.text.pdf.PRStream;
> import com.lowagie.text.pdf.PdfDictionary;
> import com.lowagie.text.pdf.PdfName;
> import com.lowagie.text.pdf.PdfObject;
> import com.lowagie.text.pdf.PdfReader;
> import com.lowagie.text.pdf.PdfStamper;
> import com.lowagie.text.pdf.PdfWriter;
> import com.lowagie.text.xml.xmp.DublinCoreSchema;
> import com.lowagie.text.xml.xmp.PdfSchema;
> import com.lowagie.text.xml.xmp.XmpArray;
> import com.lowagie.text.xml.xmp.XmpSchema;
> import com.lowagie.text.xml.xmp.XmpWriter;
>
> public class XmpMetadataTest {
>
> /**
> * Generates a PDF, RTF and HTML file with the text 'Hello World'
> with some
> * metadata.
> *
> * @param args
> * no arguments needed here
> */
> public static void main(String[] args) {
> createOriginal();
> alterXmp1();
> alterXmp2();
> }
>
> public static void createOriginal() {
> // step 1: creation of a document-object
> Document document = new Document();
> try {
> // step 2:
> PdfWriter writer = PdfWriter.getInstance(
> // that listens to the document
> document,
> // and directs a PDF-stream to a file
> new
> FileOutputStream("xmp_original.pdf"));
> // step 3: we add metadata and open the document
> ByteArrayOutputStream os = new ByteArrayOutputStream();
> XmpWriter xmp = new XmpWriter(os);
> XmpSchema dc = new DublinCoreSchema();
> XmpArray subject = new XmpArray(XmpArray.UNORDERED);
> subject.add("Hello World");
> subject.add("XMP & Metadata");
> subject.add("Metadata");
> dc.setProperty(DublinCoreSchema.SUBJECT, subject);
> xmp.addRdfDescription(dc);
> PdfSchema pdf = new PdfSchema();
> pdf.setProperty(PdfSchema.KEYWORDS, "Hello World, XMP,
> Metadata");
> pdf.setProperty(PdfSchema.VERSION, "1.4");
> xmp.addRdfDescription(pdf);
> xmp.close();
> writer.setXmpMetadata(os.toByteArray());
> document.open();
> // step 4: we add a paragraph to the document
> document.add(new Paragraph("Hello World"));
> } catch (DocumentException de) {
> System.err.println(de.getMessage());
> } catch (IOException ioe) {
> System.err.println(ioe.getMessage());
> }
>
> // step 5: we close the document
> document.close();
> }
>
> public static void alterXmp1() {
> PdfReader reader;
> try {
> reader = new PdfReader("xmp_original.pdf");
> PdfDictionary catalog = reader.getCatalog();
> PdfObject obj = catalog.get(PdfName.METADATA);
> PRStream stream = (PRStream)PdfReader.getPdfObject(obj);
> String metadata = new
> String(PdfReader.getStreamBytes(stream));
> metadata = metadata.replaceAll("Hello World", "Hello
> Universe");
> Document.compress = false;
> stream.setData(metadata.getBytes());
> Document.compress = true;
> PdfStamper stamper = new PdfStamper(reader, new
> FileOutputStream
> ("xmp_altered1.pdf"));
> stamper.close();
> } catch (IOException e) {
> e.printStackTrace();
> } catch (DocumentException e) {
> e.printStackTrace();
> }
> }
>
> public static void alterXmp2() {
> PdfReader reader;
> try {
> reader = new PdfReader("xmp_original.pdf");
> String metadata = new String(reader.getMetadata());
> metadata = metadata.replaceAll("Hello World", "Hello
> Universe");
> PdfStamper stamper = new PdfStamper(reader, new
> FileOutputStream
> ("xmp_altered2.pdf"));
> stamper.setXmpMetadata(metadata.getBytes());
> stamper.close();
> } catch (IOException e) {
> e.printStackTrace();
> } catch (DocumentException e) {
> e.printStackTrace();
> }
> }
> }---------------------------------------------------------------------
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