print pdf

[persiabudi28]

how to print pdf?

[liebki]

Like with a printer?

Edit: Maybe this XAMARIN-Case works:

https://www.syncfusion.com/kb/8767/how-to-print-pdf-documents-in-xamarin-forms-platform

[Cywizz]

The PrintManager.GetForCurrentView() is not supported for WinUI desktop applications (Used in the link above). I am struggling to find a solution to print a pdf document in .Net Maui (Windows platform).
Did anyone manage to get around the issue, or is printing just not supported at this stage?

[stipar]

yo logre imprimir en windows, lo que todavía no es posible es en android me parece

[LanceMcCarthy]

yo logre imprimir en windows, lo que todavía no es posible es en android me parece

por favor mire el resto del código en mi demostración. Funciona para todas las plataformas.

el código específico de la plataforma está en una clase parcial, el nombre del archivo dice para qué plataforma es.

[kushald7]

@stipar can you share code for printing on windows

[LanceMcCarthy]

In case it helps, I have a .NET MAUI demo that shows you how to do this using the native platform APIs to print a PDF file with a single line of code (after you've added the helper classes).

private async void PrintPdf_OnClicked(object sender, EventArgs e)
{
    var stream = await FileSystem.OpenAppPackageFileAsync("pdfviewer-overview.pdf");

    // See the 3 classes in /Helpers/ folder.
    var helper = new PrintHelper();

#if WINDOWS
    
    helper.Print(stream, "pdfviewer-overview.pdf", this.Window.Handler.PlatformView as Microsoft.UI.Xaml.Window);

#elif __IOS__ || MACCATALYST || ANDROID

    helper.Print(stream, "pdfviewer-overview.pdf");
    
#endif
}

See the project for the rest of the info => https://github.com/LanceMcCarthy/CustomMauiExamples/tree/main/src/DocumentPrinting

[stipar]

estoy probando en .net8 no funciona, alguna solucion?

[Cywizz]

Thank you @LanceMcCarthy , I will check definitely this out!

[Xyncgas]

Anyone has success printing PDF by creating a webview with 0 width height and using javascript to do it

[LanceMcCarthy]

This wont work on all platforms, because not all the native WebViews support printing via JavaScript.

You also have to consider figuring out how to get the PDF file from outside of the webview to inside of the webview without user interaction or messing up the PDF. Sure you can try some crazy conversations like serializing the byte[] to base64, then embedding the base64 into the dynamically loaded javascript code as a variable, but you can't do this for anything but trivial documents.

[Xyncgas]

You also have to consider...

Remember it's Maui, I can share memory between webview and .Net

[martinblampied]

Anyone find a work around for this?

[MichaelHall001]

I've downloaded your Printing Demo for .net MAUI. It works on Windows but I need it to work on Android. I have these squiggly red lines on line 17 and 25. Also the errors at the bottom of Visual Studio. Thoughts on this? Should it work on Android?

[LanceMcCarthy]

Heh, that's unexpected. I'm away from a PC for couple days, but I'll use Github Codespaces to debug it in a few hours to see if I can fix it sooner.

In the meantime, you can always copy/paste the code out of the Helper class file and into the code behind to use the Print() method directly.

I'll reply again once I've had a chance to review it.

[stipar]

el metodo print ya no esta disponible para android, si para las otras plataformas, seguramente no debe ser compatible con el nuevo sdk de android

[Cywizz]

I think Lance's demo is just missing a filename in the constructor if I remember correctly as he does not have a default constructor specified.
I have successfully used his code to get things going on Windows and Android (12) and have extracted it in a demo here: https://github.com/Cywizz/PrintDemo
I have yet to test it on other platforms, although the code is there.
All I changed was adding a Print Service for injection as I am using MVVM in my main project (Not this demo), and added a CanPrint() method where you can implement additional logic before the process starts. I also moved the "helper" classes into their platform specific locations.
Thanks again for the initial code Lance, I have credited you in the demo.

[LanceMcCarthy]

Thanks @Cywizz!

@MichaelHall001 I'm sorry for the delay, I was on vacation last week and GitHub CodeSpaces was not sufficient enough for me to say "yeah, it's fixed". I have updated the demo and used Cywizz's abstraction approach to surface the common naming to the MAUI layer:

You can see the new code at the following locations:

• https://github.com/LanceMcCarthy/CustomMauiExamples/blob/main/src/DocumentPrinting/DocumentPrinting/MainPage.xaml.cs
• https://github.com/LanceMcCarthy/CustomMauiExamples/blob/main/src/DocumentPrinting/DocumentPrinting/Helpers/PrintHelper.Android.cs

[MichaelHall001]

Its working LikeABo$$ OMG!!! Thanks Lance!! You are a life saver. You are the best!!!

…

On Tue, Aug 22, 2023 at 11:10 AM Lance McCarthy ***@***.***> wrote: Thanks @Cywizz <https://github.com/Cywizz>! @MichaelHall001 <https://github.com/MichaelHall001> I'm sorry for the delay, I was on vacation last week and GitHub CodeSpaces was not sufficient enough for me to say "yeah, it's fixed". I have updated the demo and used Cywizz's abstraction approach to surface the common naming to the MAUI layer: [image: image] <https://user-images.githubusercontent.com/3520532/262414624-2b7951aa-7c2d-4552-8edd-e605166a2444.png> You can see the new code at the following locations: - https://github.com/LanceMcCarthy/CustomMauiExamples/blob/main/src/DocumentPrinting/DocumentPrinting/MainPage.xaml.cs - https://github.com/LanceMcCarthy/CustomMauiExamples/blob/main/src/DocumentPrinting/DocumentPrinting/Helpers/PrintHelper.Android.cs — Reply to this email directly, view it on GitHub <#13528 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AVPFYY3FXCZQZQ3GVJEL7XDXWTKXBANCNFSM6AAAAAAVF2IULE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[MichaelHall001]

We never were able to get it working. It came up with no error messages when we compiled it after you fixed it. My client couldn't get his blue tooth printer to talk to the phone and stuff. We abandoned everything. Sorry.

…

On Thu, Sep 14, 2023 at 9:10 AM Nicolas Luza ***@***.***> wrote: @LanceMcCarthy <https://github.com/LanceMcCarthy> hello, your project works with the default pdf, but I try to put another pdf and I get System.IO.FileNotFoundException: '33_5072.pdf', it is saving in '\DocumentPrinting\DocumentPrinting\objœDebug\net7.0-android\assets', do you know what could it be? [image: image] <https://user-images.githubusercontent.com/43099709/268002798-e986471f-41e9-471d-a1a1-e2dcadb76650.png> thx — Reply to this email directly, view it on GitHub <#13528 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AVPFYY7ANYIFVK4GP675JZLX2MF5JANCNFSM6AAAAAAVF2IULE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[jaberlinz]

Hi McCarthy, I ran the project on windows and it works well.
But on android it throw this error
System.IO.DirectoryNotFoundException: 'Could not find a part of the path /data/user/0/com.companyname.mauiapp1/files/Documents/AboutAssets.txt'.'
The link you have provided does not suggest anything in relation to this behaviour.
Could you please advice further.
Thanks!

[LanceMcCarthy]

That isnt related to the demo, it means that you have a file that was supposed to be compiled with the app, but it wasn't. You can google that error and find conversations about how to handle it. Sometimes when I hit these, I'll start with a fresh project because all of the csproj stuff hasnt been borked.

Search something like ".NET MAUI 'Could not find a part of the path AboutAssets.txt', but the best place to get help with this kind of compilation issue is in the .NET Discord (the MAUI channel) => http://aka.ms/dotnet-discord

[jaberlinz]

thanks for the swift answer!
I followed this link (https://stackoverflow.com/questions/72838980/system-io-directorynotfoundexception-could-not-find-a-part-of-the-path)
it sais: please be aware that Environment.SpecialFolder.LocalApplicationData maps to /data/user/0/com.companyname.mauiapptest/files locally in MAUI.

so I got the error solved by replacing this code:
string createdFilePath = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), fileName);
with this one:
string createdFilePath = System.IO.Path.Combine(System.Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), fileName);

Now I got no errors.. thats good! : )

However, my App keep showing the loading bar (Unendlessly) with the text "Print Preview"!
I have tried both testing on the android amulator and the local Smartphone, I have tried also the default Printer and the PDF printer, no luck!

any advice is highly appreciated!
Cheers!

[jaberlinz]

Update,
The error was related to the PDF File itself (probably because its in German!)
I replaced it with the PDF given in the example and it was printed smoothly!
Thanks McCarthy for your help : )

[LanceMcCarthy]

Aha! Nice catch :)

[PrabhuRout007]

Hey! @LanceMcCarthy what if I don't want to print the pdf I want to print the image which path I am passing in a string. I am getting the file but it seems it is not getting loaded in the previewPages but the data is present is canvas children element and some how print task is not working proper, I am sharing my code can you help me out with this.

public async void Print(Stream inputStream, string filepath, Window nativeWindow)
{
_filePath = filepath;
this._fileName = Path.GetFileName(_filePath);
this._window = nativeWindow;
this._hWnd = WinRT.Interop.WindowNative.GetWindowHandle(_window);
var fileType = File.ReadAllBytes(filepath);
try
{
await PrintWithCanvas();
}
catch
{
Debug.WriteLine("No UI thread available, printing without Canvas.");
await PrintWithoutCanvas();
}
}
private async Task PrintWithCanvas()
{
await this.IncludeCanvas();
this.RegisterForPrint();
await PrintManagerInterop.ShowPrintUIForWindowAsync(_hWnd);
}
private async Task PrintWithoutCanvas()
{
this.RegisterForPrint();
await PrintManagerInterop.ShowPrintUIForWindowAsync(_hWnd);
}
private void RegisterForPrint()
{
printDocument = new PrintDocument();
printDocumentSource = printDocument.DocumentSource;
printDocument.AddPages += AddPrintPages;
printDocument.GetPreviewPage += PrintDoc_GetPreviewPage;
printDocument.Paginate += PrintDoc_Paginate;
printMan = PrintManagerInterop.GetForWindow(_hWnd);
printMan.PrintTaskRequested += PrintTask_Requested;
}
private async void AddPrintPages(object sender, AddPagesEventArgs e)
{
try
{
await this.PrepareForPrint(0,1);

            ((PrintDocument)sender).AddPagesComplete();
        }
        catch
        {
            ((PrintDocument)sender).InvalidatePreview();
        }
    }
    private async Task PrepareForPrint(int p, int count)
    {
        imagePanel.Children.Clear();
        ApplicationLanguages.PrimaryLanguageOverride = CultureInfo.InvariantCulture.TwoLetterISOLanguageName;
        var imageCtrl = new Image();
        BitmapImage src = new BitmapImage(new Uri(_filePath, UriKind.Absolute));
        imageCtrl.Source = src;
        imageCtrl.Height = src.PixelHeight / DeviceDisplay.Current.MainDisplayInfo.Density;
        imageCtrl.Width = src.PixelWidth / DeviceDisplay.Current.MainDisplayInfo.Density;
        printDocument.AddPage(imageCtrl);
    }
    private async Task IncludeCanvas()
    {
        var imageCtrl = new Image();
        BitmapImage src = new BitmapImage(new Uri(_filePath, UriKind.Absolute));
        imageCtrl.Source = src;
        imageCtrl.Height = 816;
        imageCtrl.Width = 700;
        var pageCanvas = new Canvas
        {
            Width = 816,
            Height = 700,
            VerticalAlignment = VerticalAlignment.Top,
            HorizontalAlignment = HorizontalAlignment.Center,
            Background = new SolidColorBrush(Color.FromArgb(255, 255, 255, 255)),
            Margin = new Thickness(0, 0, 0, 0)
        };
        pageCanvas.Children.Add(imageCtrl);
        imagePanel.Children.Add(pageCanvas);
    }
    private void PrintTask_Requested(PrintManager sender, PrintTaskRequestedEventArgs args)
    {
        printTask = args.Request.CreatePrintTask(_fileName, sourceRequested => sourceRequested.SetSource(printDocumentSource));
        printTask.Completed += PrintTask_Completed;
    }

    private void PrintTask_Completed(PrintTask sender, PrintTaskCompletedEventArgs args)
    {
        printTask.Completed -= PrintTask_Completed;
        printMan.PrintTaskRequested -= PrintTask_Requested;
    }

    private async void PrintDoc_Paginate(object sender, PaginateEventArgs e)
    {
        var pageDescription = e.PrintTaskOptions.GetPageDescription((uint)e.CurrentPreviewPageNumber);

        marginWidth = pageDescription.PageSize.Width;
        marginHeight = pageDescription.PageSize.Height;

        for (var i = imagePanel.Children.Count - 1; i >= 0; i--)
        {
            var print = imagePanel.Children[i] as Canvas;

            if (print == null)
                continue;

            print.Width = marginWidth;
            print.Height = marginHeight;

            this.printPreviewPages.TryAdd(i, print);
        }

    ((PrintDocument)sender).SetPreviewPageCount(_pageCount, PreviewPageCountType.Final);
    }
    private void PrintDoc_GetPreviewPage(object sender, GetPreviewPageEventArgs e)
    {
        imagePanel.Children.Remove(this.printPreviewPages[e.PageNumber - 1]);
        ((PrintDocument)sender).SetPreviewPage(e.PageNumber, this.printPreviewPages[e.PageNumber - 1]);
    }  
    
    passing the values to print parameter from here  
private void PrintClickedEvent(object sender, EventArgs e)
{
    try
    {
        var selectedImages = new List<String>();
        if (MainCanvasViewModel.CanvasImagePath != null && MainCanvasViewModel.IsCanvasHaveImage)
            selectedImages.Add(MainCanvasViewModel.CanvasImagePath);
        var filepath = selectedImages.FirstOrDefault();
        _printService = new PrintService();
        var openFile = System.IO.File.OpenRead(filepath);   

#if MACCATALYST
_printService.PrintImageMac(openFile);
#elif WINDOWS
_printService.Print(openFile, filepath, this.Window.Handler.PlatformView as Microsoft.UI.Xaml.Window);
#endif
}
catch (Exception ex)
{
LogHandler.LogError(ex);
}
}

[LanceMcCarthy]

Hi @PrabhuRout007 This workflow was specifically designed for PDF content bytes, so I can't promise it will work for other content types. That being said, I don't see why it couldn't work if the image byte content is correct and is loaded into an Image() control at runtime.

However, you may or may not see the preview correctly... so I recommend just sending it to the printer to double check if your issue is with the preview rendering or the entire setup.

Ultimately, this code originally came from Microsoft's PRinting API demo, you can refer back to that for more details on the implementation. It's more robust than this one, which was whittled down to support PDF layouts.

Here are links to two demos that implement printing:

• https://github.com/Microsoft/Windows-appsample-coloringbook
• https://github.com/microsoft/windows-universal-samples/tree/main/Samples/Printing

[PrabhuRout007]

@LanceMcCarthy Yes, although I am getting image bitmap and it is also added in the canvas as I debug I can see canvas has added the image as its children, when I print then also the print is happening smoothly, The issue is with the preview only, for first time when it is been called it has the the data but still not visible in preview although for the second time also I can the image is been displayed in canvas.

Here I had modified the code, if you found anything please let me know. Also it will help others who are facing issue in printing the image on Windows, All windows operations are working fine here except the previewPage functionality

public class PrintService
{
    private PageDescription currentPageDescription;
    private UIElement printPreviewPages;
    private Canvas imagePanel = new();
    private string _filePath;
    private Window _window;
    private string _fileName;
    private nint _hWnd;
    private PrintDocument printDocument;
    private IPrintDocumentSource printDocumentSource;
    private PrintManager printMan;
    private int _pageCount;
    private double marginWidth;
    private double marginHeight;
    private PrintTask printTask;
    private FrameworkElement firstPage;
    private PhotoSize photoSize;
    private Scaling photoScale;
    private const int DPI96 = 96;

#if MACCATALYST
public async void PrintImageMac(Stream img)
{
try
{
var data = NSData.FromStream(img);
var uiimage = UIImage.LoadFromData(data);

            var printer = UIPrintInteractionController.SharedPrintController;
            if (printer == null)
            {
                await UIUtility.ShowMessage("Printer is not connected");
            }
            else
            {
                var printInfo = UIPrintInfo.PrintInfo;
                printInfo.OutputType = UIPrintInfoOutputType.General;
                printer.PrintInfo = printInfo;
                printer.PrintingItem = uiimage;

                var handler = new UIPrintInteractionCompletionHandler((printInteractionController, completed, error) =>
                {
                    if (completed)
                    {
                        UIUtility.ShowMessage("Printer Success");
                    }
                    else if (!completed && error != null)
                    {
                        UIUtility.ShowMessage("Print Failed");
                    }
                });

                CGRect frame = new CGRect();
                frame.Size = uiimage.Size;
                printer.Present(true, handler);
            }
        }
        catch (Exception ex)
        {
            LogHandler.LogError(ex);
        }
    }

#elif WINDOWS
public async void Print(Stream inputStream, string filepath, Window nativeWindow)
{
_filePath = filepath;
this._fileName = Path.GetFileName(_filePath);
this._window = nativeWindow;
this._hWnd = WinRT.Interop.WindowNative.GetWindowHandle(_window);
var fileType = File.ReadAllBytes(filepath);
try
{
await PrintWithCanvas();
}
catch(Exception ex)
{
LogHandler.LogError(ex);
}
}
private async Task PrintWithCanvas()
{
try
{
this.RegisterForPrint();
await PrintManagerInterop.ShowPrintUIForWindowAsync(_hWnd);
}
catch (Exception ex)
{
LogHandler.LogError(ex);
}
}

    private void RegisterForPrint()
    {
        try
        {
            printDocument = new PrintDocument();
            printDocumentSource = printDocument.DocumentSource;
            printDocument.Paginate += CreatePrintPreviewPages;
            printDocument.GetPreviewPage += PrintDoc_GetPreviewPage;

            printDocument.AddPages += AddPrintPages;
            printMan = PrintManagerInterop.GetForWindow(_hWnd);
            printMan.PrintTaskRequested += PrintTask_Requested;
        }
        catch (Exception ex)
        {
            LogHandler.LogError(ex);
        }
    }
    private async void AddPrintPages(object sender, AddPagesEventArgs e)
    {
        try
        {
            await this.PrepareForPrint();

            ((PrintDocument)sender).AddPagesComplete();
        }
        catch
        {
            ((PrintDocument)sender).InvalidatePreview();
        }
    }
    private async Task PrepareForPrint()
    {
        imagePanel.Children.Clear();
        ApplicationLanguages.PrimaryLanguageOverride = CultureInfo.InvariantCulture.TwoLetterISOLanguageName;
        var imageCtrl = new Image();
        BitmapImage src = new BitmapImage(new Uri(_filePath, UriKind.Absolute));
        imageCtrl.Source = src;

        imageCtrl.Height = currentPageDescription.ViewablePageSize.Height / DeviceDisplay.Current.MainDisplayInfo.Density;
        imageCtrl.Width = currentPageDescription.ViewablePageSize.Width / DeviceDisplay.Current.MainDisplayInfo.Density;
        imageCtrl.HorizontalAlignment = Microsoft.UI.Xaml.HorizontalAlignment.Center;
        imageCtrl.VerticalAlignment = Microsoft.UI.Xaml.VerticalAlignment.Center;
        printDocument.AddPage(imageCtrl);
    }

    private async void PrintTask_Requested(PrintManager sender, PrintTaskRequestedEventArgs args)
    {
        printTask = args.Request.CreatePrintTask(_fileName, sourceRequestedArgs =>
        {
            CustomizePrintTask(args, sourceRequestedArgs).GetAwaiter();
        });
        printTask.Completed += PrintTask_Completed1;
    }

    private void PrintTask_Completed1(PrintTask sender, PrintTaskCompletedEventArgs args)
    {
        printMan.PrintTaskRequested -= PrintTask_Requested;
    }
    private async Task CustomizePrintTask(PrintTaskRequestedEventArgs args, PrintTaskSourceRequestedArgs sourceRequestedArgs)
    {
        PrintTaskOptionDetails printDetailedOptions = PrintTaskOptionDetails.GetFromPrintTaskOptions(printTask.Options);
        printDetailedOptions.DisplayedOptions.Clear();
        printDetailedOptions.DisplayedOptions.Add(Windows.Graphics.Printing.StandardPrintTaskOptions.MediaSize);
        printDetailedOptions.DisplayedOptions.Add(Windows.Graphics.Printing.StandardPrintTaskOptions.Copies);
        printDetailedOptions.DisplayedOptions.Add(Windows.Graphics.Printing.StandardPrintTaskOptions.ColorMode);

        // Create a new list option.
        PrintCustomItemListOptionDetails photoSize = printDetailedOptions.CreateItemListOption("photoSize", "Photo Size");
        photoSize.AddItem("SizeFullPage", "Full Page");
        photoSize.AddItem("Size4x6", "4 x 6 in");
        photoSize.AddItem("Size5x7", "5 x 7 in");
        photoSize.AddItem("Size8x10", "8 x 10 in");
        printDetailedOptions.DisplayedOptions.Add("photoSize");
        printTask.Options.Orientation = PrintOrientation.Portrait;
        sourceRequestedArgs.SetSource(printDocumentSource);
    }
    private async void PrintDetailedOptionsOptionChanged(PrintTaskOptionDetails sender, PrintTaskOptionChangedEventArgs args)
    {
        if (args.OptionId == null)
        {
            return;
        }

        string optionId = args.OptionId.ToString();

        if (optionId == "photoSize")
        {
            IPrintOptionDetails photoSizeOption = sender.Options[optionId];
            string photoSizeValue = photoSizeOption.Value as string;

            if (!string.IsNullOrEmpty(photoSizeValue))
            {
                switch (photoSizeValue)
                {
                    case "SizeFullPage":
                        photoSize = PhotoSize.SizeFullPage;
                        break;
                    case "Size4x6":
                        photoSize = PhotoSize.Size4x6;
                        break;
                    case "Size5x7":
                        photoSize = PhotoSize.Size5x7;
                        break;
                    case "Size8x10":
                        photoSize = PhotoSize.Size8x10;
                        break;
                }
            }
        }

        if (optionId == "scaling")
        {
            IPrintOptionDetails scalingOption = sender.Options[optionId];
            string scalingValue = scalingOption.Value as string;

            if (!string.IsNullOrEmpty(scalingValue))
            {
                switch (scalingValue)
                {
                    case "Crop":
                        photoScale = Scaling.Crop;
                        break;
                    case "ShrinkToFit":
                        photoScale = Scaling.ShrinkToFit;
                        break;
                }
            }
        }
    }
    private async void CreatePrintPreviewPages(object sender, PaginateEventArgs e)
    {
        try
        {
            PrintDocument printDoc = (PrintDocument)sender;
            PageDescription pageDescription = new PageDescription();
            //PrintTaskOptionDetails printDetailedOptions = PrintTaskOptionDetails.GetFromPrintTaskOptions(e.PrintTaskOptions);
            PrintPageDescription printPageDescription = e.PrintTaskOptions.GetPageDescription(0);
            pageDescription.Margin.Width = Math.Max(
                printPageDescription.ImageableRect.Left,
                printPageDescription.ImageableRect.Right - printPageDescription.PageSize.Width);

            pageDescription.Margin.Height = Math.Max(
                printPageDescription.ImageableRect.Top,
                printPageDescription.ImageableRect.Bottom - printPageDescription.PageSize.Height);

            pageDescription.ViewablePageSize.Width = printPageDescription.PageSize.Width - pageDescription.Margin.Width * 2;
            pageDescription.ViewablePageSize.Height = printPageDescription.PageSize.Height - pageDescription.Margin.Height * 2;

            switch (photoSize)
            {
                case PhotoSize.Size4x6:
                    pageDescription.PictureViewSize.Width = 4 * DPI96;
                    pageDescription.PictureViewSize.Height = 6 * DPI96;
                    break;
                case PhotoSize.Size5x7:
                    pageDescription.PictureViewSize.Width = 5 * DPI96;
                    pageDescription.PictureViewSize.Height = 7 * DPI96;
                    break;
                case PhotoSize.Size8x10:
                    pageDescription.PictureViewSize.Width = 8 * DPI96;
                    pageDescription.PictureViewSize.Height = 10 * DPI96;
                    break;
                case PhotoSize.SizeFullPage:
                    pageDescription.PictureViewSize.Width = pageDescription.ViewablePageSize.Width;
                    pageDescription.PictureViewSize.Height = pageDescription.ViewablePageSize.Height;
                    break;
            }
            if ((pageDescription.ViewablePageSize.Width > pageDescription.ViewablePageSize.Height) && (photoSize != PhotoSize.SizeFullPage))
            {
                var swap = pageDescription.PictureViewSize.Width;
                pageDescription.PictureViewSize.Width = pageDescription.PictureViewSize.Height;
                pageDescription.PictureViewSize.Height = swap;
            }
            pageDescription.IsContentCropped = photoScale == Scaling.Crop;
            currentPageDescription = pageDescription;
            printDoc.SetPreviewPageCount(1, PreviewPageCountType.Intermediate);
        }
        catch (Exception ex)
        {
            LogHandler.LogError(ex);
        }
        
    }
    private async void PrintDoc_GetPreviewPage(object sender, GetPreviewPageEventArgs e)
    {
        int pageNumber = e.PageNumber;
        UIElement page;
        page = await GeneratePageAsync(1, currentPageDescription);
        printPreviewPages = page;
        PrintDocument printDoc = (PrintDocument)sender;
        printDoc.SetPreviewPage(pageNumber, page);

    }
    private async Task<UIElement> GeneratePageAsync(int photoNumber, PageDescription pageDescription)
    {
        Canvas viewablePage = new Canvas()
        {
            Width = pageDescription.ViewablePageSize.Width,
            Height = pageDescription.ViewablePageSize.Height
        };

        var imageCtrl = new Image();
        BitmapImage src = new BitmapImage(new Uri(_filePath, UriKind.Absolute));
        imageCtrl.Source = src;

        imageCtrl.Height = currentPageDescription.ViewablePageSize.Height / DeviceDisplay.Current.MainDisplayInfo.Density;
        imageCtrl.Width = currentPageDescription.ViewablePageSize.Width / DeviceDisplay.Current.MainDisplayInfo.Density;
        imageCtrl.HorizontalAlignment = Microsoft.UI.Xaml.HorizontalAlignment.Center;
        imageCtrl.VerticalAlignment = Microsoft.UI.Xaml.VerticalAlignment.Center;

        viewablePage.Children.Add(imageCtrl);
        return viewablePage;
    }
    private static void Swap<T>(ref T v1, ref T v2)
    {
        T swap = v1;
        v1 = v2;
        v2 = swap;
    }

#endif
}
}
public class PageDescription : IEquatable
{
public Size Margin;
public Size PageSize;
public Size ViewablePageSize;
public Size PictureViewSize;
public bool IsContentCropped;

public bool Equals(PageDescription other)
{
    // Detect if PageSize changed
    bool equal = (Math.Abs(PageSize.Width - other.PageSize.Width) < double.Epsilon) &&
        (Math.Abs(PageSize.Height - other.PageSize.Height) < double.Epsilon);

    // Detect if ViewablePageSize changed
    if (equal)
    {
        equal = (Math.Abs(ViewablePageSize.Width - other.ViewablePageSize.Width) < double.Epsilon) &&
            (Math.Abs(ViewablePageSize.Height - other.ViewablePageSize.Height) < double.Epsilon);
    }
    // Detect if PictureViewSize changed
    if (equal)
    {
        equal = (Math.Abs(PictureViewSize.Width - other.PictureViewSize.Width) < double.Epsilon) &&
            (Math.Abs(PictureViewSize.Height - other.PictureViewSize.Height) < double.Epsilon);
    }
    // Detect if cropping changed
    if (equal)
    {
        equal = IsContentCropped == other.IsContentCropped;
    }
    return equal;
}

}
public enum PhotoSize : byte
{
SizeFullPage,
Size4x6,
Size5x7,
Size8x10
}
public enum Scaling : byte
{
ShrinkToFit,
Crop
}

[LanceMcCarthy]

Try dispatching the Preview-rendering cycle to the UI thread. I removed that to keep my example simple. You can also go to the original Microsoft demo to see the full implementation.