DynamicPDF Blog

XMP metadata is a powerful tool for describing the contents of a PDF document. DynamicPDF has built in support for many of the most popular schemas:

• Dublin Core Schema
• Basic Schema
• Rights Management Schema
• Basic Job Ticket Schema
• Paged-Text Schema
• Adobe PDF Schema

However, there are times when you may need to embed other metadata in a PDF. This can easily be done by creating a class that inherits from the XmpSchema base class and overriding the Draw method. This Draw method will then be called when the XMP metadata is being added to the PDF. First let’s define a CustomSchema class that inherits from XmpSchema:

class CustomSchema : XmpSchema
{
    private string userName;
    private DateTime creationDate;

    public CustomSchema(string userName, DateTime creationDate)
    {
        this.userName = userName;
        this.creationDate = creationDate;
    }

    protected override void Draw(XmpWriter xmpWriter)
    {
        xmpWriter.BeginDescription("http://ns.adobe.com/xap/1.0/", "xmp", " ");
        if (userName != null) xmpWriter.Draw("\t\t" + userName + "\n");
        xmpWriter.Draw("\t\t" + creationDate.ToString("yyyy-MM-dd'T'HH:mm:sszzz") + "\n");
        xmpWriter.Draw("\t\t" + xmpWriter.Producer + "\n");
        xmpWriter.Draw("\t\t" + xmpWriter.Date.ToLocalTime().ToString("yyyy-MM-dd'T'HH:mm:sszzz") + "\n");
        xmpWriter.EndDescription();
    }
}

Notice that the Draw method starts by calling the BeginDescription method and ends by calling the EndDescription method. XMP metadata is XML based, and these methods are responsible for the opening and closing XML tags for the custom schema. The Draw method that is called multiple times between them is then responsible for outputting the other XML data.

Next, we will add the CustomSchema class we created to the XMP metatdata of the document:

XmpMetadata xmpMetadata = new XmpMetadata();
xmpMetadata.AddSchema(new CustomSchema("John", DateTime.Now));
document.XmpMetadata = xmpMetadata;

The following custom metatdata will now appear in the PDFs XMP metadata:

<rdf:Description rdf:about=' ' xmlns:xmp='http://ns.adobe.com/xap/1.0/'>
    <xmp:CreatedBy>John</xmp:CreatedBy>
    <xmp:DateCreated>2019-06-03T16:18:17-04:00</xmp:DateCreated>
    <xmp:CreatorTool>DynamicPDF for .NET v10.12.0.40 (Build 38759)</xmp:CreatorTool>
    <xmp:MetadataDate>2019-06-03T16:18:17-04:00</xmp:MetadataDate>
</rdf:Description>

Wrap Up

A C# Visual Studio project demonstrating this is available on GitHub:

https://github.com/DynamicPDF/dotnet-custom-xmp-schemas

If you have any questions or comments, I would love to hear from you.