Introduction

Efficiently converting documents to HTML while preserving their integrity and adding security features like watermarks is a common requirement in modern applications. This tutorial will guide you through using GroupDocs.Viewer for .NET to render documents into HTML with embedded resources and seamlessly add watermarks.

Document Rendering with GroupDocs.Viewer .NET

You will learn how to:

  • Set up and use GroupDocs.Viewer for .NET.
  • Render documents to HTML with all resources embedded.
  • Add a text watermark to your rendered documents.
  • Apply best practices for performance and security.

Prerequisites

Before you begin, ensure you have the following:

  • .NET SDK: Installed on your machine.
  • IDE: Visual Studio or another .NET development environment.
  • GroupDocs.Viewer for .NET: Version 25.3.0 or later. You can install it via NuGet.
  • Basic Knowledge: A solid understanding of C# and the .NET framework.

Install via NuGet

Use the following command in your Package Manager Console:

Install-Package GroupDocs.Viewer -Version 25.3.0

Or via the .NET CLI:

dotnet add package GroupDocs.Viewer --version 25.3.0

Licensing

GroupDocs.Viewer for .NET requires a license for full functionality. You can get a free temporary license for evaluation or purchase a full license.

Render to HTML with a Watermark

This guide will walk you through the process of rendering a document to HTML and adding a watermark.

Step 1: Define Output Directory and File Path Format

First, specify the directory where the rendered HTML files will be saved and the format for the output file names.

using System.IO;

// Define the output directory
string outputDirectory = "YOUR_OUTPUT_DIRECTORY";

// Define the format for the output file path
string pageFilePathFormat = Path.Combine(outputDirectory, "page_{0}.html");

Note: Replace YOUR_OUTPUT_DIRECTORY with your desired path.

Step 2: Configure HTML View Options with a Watermark

Create an instance of HtmlViewOptions and set the watermark text.

using GroupDocs.Viewer.Options;

// Create HTML view options for embedded resources
HtmlViewOptions options = HtmlViewOptions.ForEmbeddedResources(pageFilePathFormat);

// Add a watermark
options.Watermark = new Watermark("This is a watermark");

Explanation: The ForEmbeddedResources method ensures that all resources like images and fonts are embedded directly into the HTML file. The Watermark property allows you to add a text or image watermark to the rendered output.

Step 3: Load and Render the Document

Initialize the Viewer object with your document and call the View() method with the configured options.

using GroupDocs.Viewer;

// Path to your document
string documentPath = "YOUR_DOCUMENT_DIRECTORY/SAMPLE.docx";

try
{
    using (Viewer viewer = new Viewer(documentPath))
    {
        // Render the document to HTML with the watermark
        viewer.View(options);
    }
    
    System.Console.WriteLine("\nSource document rendered successfully.\nCheck output in {0}", outputDirectory);
}
catch (System.Exception exp)
{
    System.Console.WriteLine("Exception: " + exp.Message);
}

Troubleshooting: Ensure that the file paths are correct and that your application has write permissions to the output directory.

Practical Applications

  • Web Document Previews: Display document previews on a corporate intranet or customer portal with a “Confidential” watermark.
  • Secure Document Sharing: Protect sensitive information by embedding watermarks before sharing rendered documents.
  • Content Management Systems: Integrate document rendering with watermarking capabilities directly into your CMS.

Performance Considerations

  • Resource Management: Use a using statement to ensure the Viewer object is properly disposed of.
  • Batch Processing: For multiple documents, consider rendering them in batches to reduce overhead.
  • Caching: Implement caching for frequently accessed documents to improve performance.

Conclusion

You have now learned how to render documents to HTML with embedded resources and add watermarks using GroupDocs.Viewer for .NET. These features are essential for building robust and secure document management solutions. As a next step, experiment with different watermark configurations, such as using an image instead of text.

FAQ Section

1. What is GroupDocs.Viewer for .NET used for?

It is a powerful library for converting over 170 document formats into HTML, PDF, and images, with options for customization like watermarking.

2. How do I install GroupDocs.Viewer for my project?

You can install it via NuGet using the Install-Package GroupDocs.Viewer command.

3. Can I use GroupDocs.Viewer without a license?

Yes, but a trial watermark will be added to the output. A temporary or full license is required for unrestricted use.

4. How do I embed resources in the HTML output?

Use the HtmlViewOptions.ForEmbeddedResources method to ensure all document elements are included in the rendered HTML.

5. Can I use an image as a watermark?

Yes, the Watermark class also accepts an image path or stream.

Resources