Show thumbnails of XPS documents

• Download demo - 7.51 KB
• Download source code - 14.1 KB

Introduction

This application was designed as a proof of concept for generating thumbnails/images from an XPS document.

Background

Recently, I came across a requirement for displaying thumbnails of XPS documents in a SharePoint document library. As a hardcore developer, I'm not in favor of readymade third-party components unless and until you really need them. Hence, I decided to create an image generator myself. I explored the native .NET methods for reading XPS documents. After exploring, I found that in .NET Framework 3.0, there is a managed DLL called ReachFramework.dll, which has all the necessary classes and methods for reading and writing XPS documents.

Classes

XpsThumbnail Class

This is the one and only class which actually generates the thumbnails from XPS documents using the GenerateThumbnail method:

converter.GenerateThumbnail();

Properties

Complete Class Listing

/// <summary>
/// Provides methods for converting XPS document in to various image format
/// </summary>
public class XpsImage
{
    private BitmapEncoder bitmapEncoder = null;
    /// <summary>
    /// Default constructor
    /// </summary>
    public XpsImage()
    {
    }

    /// <summary>
    /// Sets the XPS file to be read
    /// </summary>
    public String XpsFileName { private get; set; }

    /// <summary>
    /// Gets or Sets the image format for thumbnail
    /// </summary>
    public OutputFormat OutputFormat {get; set; }

    /// <summary>
    /// Gets or Sets the image quality for thumbnail
    /// </summary>
    public OutputQuality OutputQuality { private get; set; }
    
    /// <summary>
    /// Returns the Memory stream of generated thumbnail
    /// </summary>
    public MemoryStream OutputStream { get; private set; }

    /// <summary>
    /// Generate the thumbnail of given document
    /// and populates the ThumbnailStream property
    /// </summary>
    public void GenerateThumbnail()
    {
        XpsDocument xpsDocument = 
          new XpsDocument(this.XpsFileName, FileAccess.Read);
        FixedDocumentSequence documentPageSequence = 
          xpsDocument.GetFixedDocumentSequence();
        
        string fileNameWithoutExtension = 
          Path.GetFileNameWithoutExtension(this.XpsFileName);
        string fileExtension = string.Empty;

        switch (this.OutputFormat)
        {
            case OutputFormat.Jpeg:
                fileExtension = ".jpg";
                bitmapEncoder = new JpegBitmapEncoder();
                break;
            case OutputFormat.Png:
                fileExtension = ".png";
                bitmapEncoder = new PngBitmapEncoder();
                break;
            case OutputFormat.Gif:
                fileExtension = ".gif";
                bitmapEncoder = new GifBitmapEncoder();
                break;
            default:
                fileExtension = ".jpg";
                bitmapEncoder = new JpegBitmapEncoder();
                break;
        }
        
        double imageQualityRatio = 1.0;
        switch (this.OutputQuality)
        {
            case OutputQuality.Low:
                imageQualityRatio /= 2.0;
                break;

            case OutputQuality.Good:
                imageQualityRatio *= 2.0;
                break;

            case OutputQuality.Super:
                imageQualityRatio *= 3.0;
                break;
            default:
                imageQualityRatio *= 1.0;
                break;
        }

        DocumentPage documentPage = 
           documentPageSequence.DocumentPaginator.GetPage(0);
        RenderTargetBitmap targetBitmap = new RenderTargetBitmap(
          (int)(documentPage.Size.Width * imageQualityRatio), 
          (int)(documentPage.Size.Height * imageQualityRatio), 
          96.0 * imageQualityRatio, 96.0 * imageQualityRatio, 
          PixelFormats.Pbgra32);
        targetBitmap.Render(documentPage.Visual);

        bitmapEncoder.Frames.Add(BitmapFrame.Create(targetBitmap));
        string str4 = string.Format("{0}{1}", 
                       fileNameWithoutExtension, fileExtension);
        MemoryStream memoryStream = new MemoryStream();
        bitmapEncoder.Save(memoryStream);
        this.OutputStream = memoryStream;
        xpsDocument.Close();
    }
}

Using the Code

The class itself is a very simple class and is made for simplicity. Below is a small snippet of how to utilize the class:

converter.XpsFileName = "XPSdocument.xps";
converter.OutputFormat = OutputFormat.Png;
converter.OutputQuality = OutputQuality.Super;
converter.GenerateThumbnail();

Conclusion

The sample application provided with this article demonstrates the utilization of the code. In the demo application, you need to save the image by invoking a context menu from the thumbnail to see the output as I'm using an in-memory image stream to display the image on the picture box.

And, please don't hesitate to provide feedback, good or bad! I hope you enjoyed this article.