如何在XAML生成的XPS中嵌入JPEG图像？

Question

I'm generating an XPS file on the fly using the XpsDocument class. In my XAML template I embed a JPEG image in an Image container. However, the embedded images in the resulting XPS are always PNG images - resulting in a very large files for certain types of images.

It seems the document writer interprets the rendered images as bitmaps and then saves them as PNG .

Here's the code that produces the XPS :

void ConvertToXps(IEnumerable<FixedDocument> fixedDocuments, Stream outputStream)
{
    var package = Package.Open(outputStream, FileMode.Create);
    var xpsDoc = new XpsDocument(package, CompressionOption.Normal);
    var xpsWriter = XpsDocument.CreateXpsDocumentWriter(xpsDoc);

    // XPS documents are built using fixed document sequences.
    var fixedDocSeq = new FixedDocumentSequence();

    // A4 = 210 x 297 mm = 8.267 x 11.692 inches = 793.632 * 1122.432 dots
    fixedDocSeq.DocumentPaginator.PageSize = new Size(793.632, 1122.432);

    foreach (var fixedDocument in fixedDocuments)
    {
        var docRef = new DocumentReference();
        docRef.BeginInit();
        docRef.SetDocument(fixedDocument);
        docRef.EndInit();
        ((IAddChild)fixedDocSeq).AddChild(docRef);
    }

    // Write out our fixed document to XPS.
    xpsWriter.Write(fixedDocSeq.DocumentPaginator);

    xpsDoc.Close();
    package.Close();
}

Q: How can I force my XAML rendered images to be saved as JPEG in the generated XPS ?

Answer 1

I think you have to change the way you create your XPS document.

var package = Package.Open(outputStream, FileMode.Create);
var xpsDoc = new XpsDocument(package, CompressionOption.Normal);
var xpsWriter = xpsDoc.AddFixedDocumentSequence();

var fixedDocSeq = xpsDoc.GetFixedDocumentSequence();

// A4 = 210 x 297 mm = 8.267 x 11.692 inches = 793.632 * 1122.432 dots
fixedDocSeq.DocumentPaginator.PageSize = new Size(793.632, 1122.432);

foreach (var fixedDocument in fixedDocuments)
{
    var docWriter = xpsWriter.AddFixedDocument();

    var pageWriter = docWriter.AddFixedPage();

    var image = pageWriter.AddImage(XpsImageType.JpegImageType);

    Stream imageStream = image.GetStream();

    //Write your image to stream

    //Write the rest of your document based on the fixedDocument object
}

The key here is getting the IXpsFixedPageWriter with the docWriter.AddFixedPage(); . This allows you to recreate your document, adding the images where you want them to be.

Not sure you can edit the already created FixedDocument unfortunately.