Extensible Metadata Platform - XMP

The Extensible Metadata Platform (XMP) is a standard created by Adobe Systems Inc. This standard was developed to process and store standardized and proprietary metadata. This metadata can be embedded into different file formats, but in this article we’ll focus only on PDF file format. We’ll see how we can embed Meta data in a PDF file using Aspose.Pdf.Facades namespace in Aspose.PDF for .NET. We’ll use PdfXmpMetadata class to manipulate XMP in the PDF document.

Background

A PDF file goes through many stages during its life time. We create a PDF document and then pass it on to other people or departments for further processing. However, during this process we need to keep track of different aspects of the changes made. XMP serves this purpose of keeping track of the changes or other information about the data in the file.

Explanation

In order to manipulate XMP using Aspose.Pdf.Facades, we will use PdfXmpMetadata class. We will use this class to manipulate predefined Meta data properties.PdfXmpMetadata class adds these properties to a PDF file. It also helps to open and save PDF files in which we’re adding Meta data. So, using PdfXmpMetadata class, we can easily manipulate XMP in a PDF file. Following code snippet will help you understand how to use PdfXmpMetadata class to work with XMP:

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET

public static void AddXmpMetadata()
{
    // The path to the documents directory
    string dataDir = RunExamples.GetDataDir_AsposePdfFacades_TechnicalArticles();

    // Create an object of PdfXmpMetadata class
    var xmpMetaData = new Aspose.Pdf.Facades.PdfXmpMetadata();

    // Create input and output file streams
    using (var input = new FileStream(dataDir + "FilledForm.pdf", FileMode.Open))
    {
        using (var output = new FileStream(dataDir + "xmp_out.pdf", FileMode.Create))
        {
            // Set input file stream
            xmpMetaData.BindPdf(input);

            // Add base URL property to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.BaseURL, "xmlns:pdf=http:// Ns.adobe.com/pdf/1.3/");

            // Add creation date property to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.CreateDate, DateTime.Now.ToString());

            // Add Metadata Date property to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.MetadataDate, DateTime.Now.ToString());

            // Add Creator Tool property to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.CreatorTool, "Creator Tool Name");

            // Add Modify Date to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.ModifyDate, DateTime.Now.ToString());

            // Add Nick Name to xmp metadata
            xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.Nickname, "Test");

            // Save xmp meta data in the pdf file
            xmpMetaData.Save(output);
        }
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET

public static void AddXmpMetadata()
{
    // The path to the documents directory
    string dataDir = RunExamples.GetDataDir_AsposePdfFacades_TechnicalArticles();

    // Create an object of PdfXmpMetadata class
    var xmpMetaData = new Aspose.Pdf.Facades.PdfXmpMetadata();

    // Create input and output file streams
    using var input = new FileStream(dataDir + "FilledForm.pdf", FileMode.Open);

    using var output = new FileStream(dataDir + "xmp_out.pdf", FileMode.Create);

    // Set input file stream
    xmpMetaData.BindPdf(input);

    // Add base URL property to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.BaseURL, "xmlns:pdf=http:// Ns.adobe.com/pdf/1.3/");

    // Add creation date property to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.CreateDate, DateTime.Now.ToString());

    // Add Metadata Date property to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.MetadataDate, DateTime.Now.ToString());

    // Add Creator Tool property to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.CreatorTool, "Creator Tool Name");

    // Add Modify Date to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.ModifyDate, DateTime.Now.ToString());

    // Add Nick Name to xmp metadata
    xmpMetaData.Add(Aspose.Pdf.Facades.DefaultMetadataProperties.Nickname, "Test");

    // Save xmp meta data in the pdf file
    xmpMetaData.Save(output);
}

Conclusion

In this article, we have seen how we can work with XMP using Aspose.Pdf.Facades. PdfXmpMetadata, used in this article, makes it very easy for the user to manipulate metadata in a PDF document. If PdfXmpMetadata class is used properly, it’ll be very easy to incorporate intelligence in the PDF files, and bringing semantic web a little bit closer to realization.