UWP WebView 打印显示打印页面模糊

Question

网上有很多关于 WebVeiw 网页打印的投诉（例如 this one and this 一个），其中打印的页面只显示屏幕上的当前视图，而不是整个页面。通过在线搜索的一些代码，我能够使用以下代码打印整个页面。但是打印页面已尝试在启用滚动条的情况下将其全部打印在一页中。而且打印出来的内容很模糊（如下图）

问题：如何在启用滚动条的情况下打印出整页内容而不模糊？

WebView中使用的网站：Wikipedia

参考：WebView to WebViewBrush

MainPage.xaml:

<Page
    x:Class="UWP_WebViewPrinting.MainPage"
    ....>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <WebView x:Name="wvTest" Source="https://en.wikipedia.org/wiki/Universal_Windows_Platform" Grid.Row="1" Margin="0,61,0,0"/>
        <Button x:Name="btnTest" Content="Test" Grid.Row="0"  VerticalAlignment="Top" Click="btnTest_Click"/>
        <Rectangle x:Name="RectangleToPrint" Grid.Row="1"/>
    </Grid>
</Page>

MainPage.xaml.cs:

private async void btnTest_Click(object sender, RoutedEventArgs e)
{
    //Step 1: use WebViewBrush to render the content of webview into the Rectangle
    int width;
    int height;
    // get the total width and height
    var widthString = await wvTest.InvokeScriptAsync("eval", new[] { "document.body.scrollWidth.toString()" });
    var heightString = await wvTest.InvokeScriptAsync("eval", new[] { "document.body.scrollHeight.toString()" });

    if (!int.TryParse(widthString, out width))
    {
        throw new Exception("Unable to get page width");
    }
    if (!int.TryParse(heightString, out height))
    {
        throw new Exception("Unable to get page height");
    }

    // resize the webview to the content
    wvTest.Width = width;
    wvTest.Height = height;

    WebViewBrush b = new WebViewBrush();
    b.SourceName = "wvTest";
    b.Redraw();
    RectangleToPrint.Fill = b;

    //Step 2: Then print the rectangle
    if (PrintManager.IsSupported())
    {
        try
        {
            // Show print UI
            await PrintManager.ShowPrintUIAsync();
        }
        catch
        {
            // Printing cannot proceed at this time
            ContentDialog noPrintingDialog = new ContentDialog()
            {
                Title = "Printing error",
                Content = "\nSorry, printing can' t proceed at this time.",
                PrimaryButtonText = "OK"
            };
            await noPrintingDialog.ShowAsync();
        }
    }
    else
    {
        // Printing is not supported on this device
        ContentDialog noPrintingDialog = new ContentDialog()
        {
            Title = "Printing not supported",
            Content = "\nSorry, printing is not supported on this device.",
            PrimaryButtonText = "OK"
        };
        await noPrintingDialog.ShowAsync();
    }
}

#region Register for printing

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    // Register for PrintTaskRequested event
    printMan = PrintManager.GetForCurrentView();
    printMan.PrintTaskRequested += PrintTaskRequested;

    // Build a PrintDocument and register for callbacks
    printDoc = new PrintDocument();
    printDocSource = printDoc.DocumentSource;
    printDoc.Paginate += Paginate;
    printDoc.GetPreviewPage += GetPreviewPage;
    printDoc.AddPages += AddPages;
}

#endregion

#region Showing the print dialog

private void PrintTaskRequested(PrintManager sender, PrintTaskRequestedEventArgs args)
{
    // Create the PrintTask.
    // Defines the title and delegate for PrintTaskSourceRequested
    var printTask = args.Request.CreatePrintTask("Print", PrintTaskSourceRequrested);

    // Handle PrintTask.Completed to catch failed print jobs
    printTask.Completed += PrintTaskCompleted;
}

private void PrintTaskSourceRequrested(PrintTaskSourceRequestedArgs args)
{
    // Set the document source.
    args.SetSource(printDocSource);
}

#endregion

#region Print preview

private void Paginate(object sender, PaginateEventArgs e)
{
    // As I only want to print one Rectangle, so I set the count to 1
    printDoc.SetPreviewPageCount(1, PreviewPageCountType.Final);
}

private void GetPreviewPage(object sender, GetPreviewPageEventArgs e)
{
    // Provide a UIElement as the print preview.
    printDoc.SetPreviewPage(e.PageNumber, this.RectangleToPrint);
}

#endregion

#region Add pages to send to the printer

private void AddPages(object sender, AddPagesEventArgs e)
{
    printDoc.AddPage(this.RectangleToPrint);

    // Indicate that all of the print pages have been provided
    printDoc.AddPagesComplete();
}

#endregion

#region Print task completed

private async void PrintTaskCompleted(PrintTask sender, PrintTaskCompletedEventArgs args)
{
    // Notify the user when the print operation fails.
    if (args.Completion == PrintTaskCompletion.Failed)
    {
        await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, async () =>
        {
            ContentDialog noPrintingDialog = new ContentDialog()
            {
                Title = "Printing error",
                Content = "\nSorry, failed to print.",
                PrimaryButtonText = "OK"
            };
            await noPrintingDialog.ShowAsync();
        });
    }
}

#endregion

打印的 PDF：可用 here

更新:

@Faywang - MSFT 的回应似乎很有希望。我尝试如下：

使用来自 here

OnPrintButtonClick()

PrintWebView()

添加了上面 post 中显示的所有其他 methods/events。
在我的btnTest_Click(...)中，我修改了用户@Faywang的代码如下

.

List<Rectangle> allpages = await GetWebPages(wvTest, new Windows.Foundation.Size(750d, 950d));
//print these pages
foreach (Rectangle rectangle in allpages)
   PrintWebView();

当应用程序在默认模式下运行时，它显示 allpages 的计数为 7，上面的 foreach 调用 PrintWebView() 7 次。如果我将应用程序屏幕置于最大模式，allpages 的计数为 3 并且 foreach 调用 PrintWebView() 3 次（如预期）。在这两种情况下，我都期望循环的最后一次迭代将带来打印对话框并打印所有第 7 页（或第 3 页，具体取决于应用程序屏幕的默认或最大模式）。相反，调试器转到 PrintWebView() 方法的 catch 块，如前所述，其代码取自 here
问题：我是否按照上述步骤正确操作？如果没有，什么是更好的方法？

Answer 1

将webview压缩重绘到矩形后会变得模糊，最好分页显示。首先我给打印页面的宽度和高度为750、950，然后根据比例来计算需要多少页。之后，您可以打印这些矩形。例如：

private async void btnTest_Click(object sender, RoutedEventArgs e)
{
    allPages = await GetWebPages(wvTest, new Windows.Foundation.Size(750d, 950d));
    //print these pages
}

async Task<List<Windows.UI.Xaml.Shapes.Rectangle>> GetWebPages(Windows.UI.Xaml.Controls.WebView webView, Windows.Foundation.Size page)
{
    // ask the content its width
    var _WidthString = await webView.InvokeScriptAsync("eval",
                new[] { "document.body.scrollWidth.toString()" });
    int _ContentWidth;
    if (!int.TryParse(_WidthString, out _ContentWidth))
        throw new Exception(string.Format("failure/width:{0}", _WidthString));
    webView.Width = _ContentWidth;

    // ask the content its height
    var _HeightString = await webView.InvokeScriptAsync("eval",
                new[] { "document.body.scrollHeight.toString()" });
    int _ContentHeight;
    if (!int.TryParse(_HeightString, out _ContentHeight))
        throw new Exception(string.Format("failure/height:{0}", _HeightString));
    webView.Height = _ContentHeight;

    // how many pages will there be?
    var _Scale = page.Width / _ContentWidth;
    var _ScaledHeight = (_ContentHeight * _Scale);
    var _PageCount = (double)_ScaledHeight / page.Height;
    _PageCount = _PageCount + ((_PageCount > (int)_PageCount) ? 1 : 0);

    // create the pages
    var _Pages = new List<Windows.UI.Xaml.Shapes.Rectangle>();
    for (int i = 0; i < (int)_PageCount; i++)
    {
        var _TranslateY = -page.Height * i;
        var _Page = new Windows.UI.Xaml.Shapes.Rectangle
        {
            Height = page.Height,
            Width = page.Width,
            Margin = new Windows.UI.Xaml.Thickness(5),
            Tag = new Windows.UI.Xaml.Media.TranslateTransform { Y = _TranslateY },
        };
        _Page.Loaded += async (s, e) =>
        {
            var _Rectangle = s as Windows.UI.Xaml.Shapes.Rectangle;
            var _Brush = await GetWebViewBrush(webView);
            _Brush.Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill;
            _Brush.AlignmentY = Windows.UI.Xaml.Media.AlignmentY.Top;
            _Brush.Transform = _Rectangle.Tag as Windows.UI.Xaml.Media.TranslateTransform;
            _Rectangle.Fill = _Brush;
        };
        _Pages.Add(_Page);
    }
    return _Pages;
}

async Task<WebViewBrush> GetWebViewBrush(Windows.UI.Xaml.Controls.WebView webView)
{
    // resize width to content
    var _OriginalWidth = webView.Width;
    var _WidthString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" });
    int _ContentWidth;
    if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
    webView.Width = _ContentWidth;

    // resize height to content
    var _OriginalHeight = webView.Height;
    var _HeightString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" });
    int _ContentHeight;
    if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
    webView.Height = _ContentHeight;

    // create brush
    var _OriginalVisibilty = webView.Visibility;
    webView.Visibility = Windows.UI.Xaml.Visibility.Visible;
    var _Brush = new WebViewBrush
    {
        SourceName = webView.Name,
        Stretch = Windows.UI.Xaml.Media.Stretch.Uniform
    };
    _Brush.Redraw();

    // reset, return
    webView.Width = _OriginalWidth;
    webView.Height = _OriginalHeight;
    webView.Visibility = _OriginalVisibilty;
    return _Brush;
}

UWP WebView 打印显示打印页面模糊

UWP WebView Printing shows the printed page blurred

c#

webview

uwp

windows-community-toolkit