c# - 在 UWP 应用程序中将 XAML 转换为 PDF

Question

我在我的 UWP 应用程序中用作打印根的 XAML 页面上有一个 Canvas 元素。我正在使用 PrintManager.PrintTaskRequested 和 PrintDocument.Paginate 等事件来准备我的报告并将其发送到打印机。

我需要以编程方式将报告导出为 PDF 文件。理想的解决方案是以某种方式利用现有的打印根( Canvas )，打印到它，然后将结果转换为 PDF。之后，我就可以将 PDF 保存到文件或将其附加到电子邮件中。

一段时间以来，我一直在寻找合适的解决方案，但在 UWP 中没有任何效果。例如，这篇文章提供了一个完美的解决方案，它似乎在 UWP 中不起作用:

How to programmatically print to PDF file without prompting for filename in C# using the Microsoft Print To PDF printer that comes with Windows 10

如有任何帮助，我将不胜感激。

Answer 1

我为这个问题苦苦挣扎了很长时间 - 在 UWP 中自动、程序化 XAML 到 PDF 的转换 - 最后找到了一个很好的解决方案。

有几个库可用于在 UWP 中以编程方式创建 PDF。诀窍是 XAML 转换。我采取了以下方法:

A) 遍历 XAML 树并生成要转换的控件列表。在我的例子中，文本 block 和边框，但这可以扩展。

B) 声明与 XAML 的实际大小相匹配的 PDF 页面大小。

C) 遍历列表，获取控件坐标。使用 C1PDF 中的适当函数在 PDF 中创建相同的元素。此代码还会检查任何 RotateTransforms 并将旋转角度也应用于文本。

使用此解决方案，我能够生成与 XAML UI 完全相似的文件(它本身代表打印文档)作为 PDF，完全可扩展且具有完美的打印渲染。

这里有一些代码可以帮助您使用我编写的 ComponentOne PDF 控件将我的 XAML 控件转换为 PDF:

Async Function XAMLtoPDF(myXAMLcontrol As Control) As Task(Of Boolean)
    Dim pdf As C1PdfDocument
    pdf = New C1PdfDocument(PaperKind.Letter)
    Dim lTB As New List(Of Object)

    pdf.PageSize = New Size(myXAMLcontrol.ActualWidth, myXAMLcontrol.ActualHeight)

    FindTextBlocks(myXAMLcontrol, lTB)
    For x = 0 To lTB.Count - 1
        If TypeOf lTB(x) Is TextBlock Then
            Dim TB As TextBlock = lTB(x)
            Dim obj As FrameworkElement = TB
            Dim angle As Double = 0
            Do While obj IsNot Nothing
                Dim renderxform As Transform = obj.RenderTransform
                If TypeOf renderxform Is TransformGroup Then
                    Dim tg As TransformGroup = CType(renderxform, TransformGroup)
                    For Each t As Transform In tg.Children
                        If TypeOf t Is RotateTransform Then
                            angle -= CType(t, RotateTransform).Angle
                        End If
                    Next
                ElseIf TypeOf renderxform Is RotateTransform Then
                    angle -= CType(renderxform, RotateTransform).Angle
                End If
                obj = obj.Parent
            Loop

            Dim myfont As Font
            Select Case TB.FontStyle
                Case FontStyle.Normal
                    If TB.FontWeight.Weight = FontWeights.Bold.Weight Then
                        myfont = New Font(TB.FontFamily.Source, TB.FontSize, PdfFontStyle.Bold)
                    Else
                        myfont = New Font(TB.FontFamily.Source, TB.FontSize, PdfFontStyle.Regular)
                    End If
                Case Else  'FontStyle.Oblique, FontStyle.Italic             '
                    myfont = New Font(TB.FontFamily.Source, TB.FontSize, PdfFontStyle.Italic)
            End Select

            Dim ttv As GeneralTransform = TB.TransformToVisual(myXAMLcontrol)
            Dim ScreenCoords As Point = ttv.TransformPoint(New Point(0, 0))
            Dim myWidth As Double, myHeight As Double
            If TB.TextWrapping = TextWrapping.NoWrap Then
                myWidth = pdf.MeasureString(TB.Text, myfont).Width
                myHeight = pdf.MeasureString(TB.Text, myfont).Height
            Else
                myWidth = TB.ActualWidth + 10       'Admittedly, 10 is a kluge factor to make wrapping match'
                myHeight = pdf.MeasureString(TB.Text, myfont, myWidth).Height
            End If
            Dim rc As New Rect(ScreenCoords.X, ScreenCoords.Y, myWidth, myHeight)

            If angle Then
                Dim fmt As New StringFormat()
                fmt.Angle = angle
                pdf.DrawString(TB.Text, myfont, CType(TB.Foreground, SolidColorBrush).Color, rc, fmt)
            Else
                pdf.DrawString(TB.Text, myfont, CType(TB.Foreground, SolidColorBrush).Color, rc)
            End If
        ElseIf TypeOf lTB(x) Is Border Then
            Dim BDR As Border = lTB(x)
            Dim ttv As GeneralTransform = BDR.TransformToVisual(myXAMLcontrol)
            Dim ScreenCoords As Point = ttv.TransformPoint(New Point(0, 0))
            Dim pts() As Point = {
                New Point(ScreenCoords.X, ScreenCoords.Y),
                New Point(ScreenCoords.X + BDR.ActualWidth, ScreenCoords.Y),
                New Point(ScreenCoords.X + BDR.ActualWidth, ScreenCoords.Y + BDR.ActualHeight),
                New Point(ScreenCoords.X, ScreenCoords.Y + BDR.ActualHeight)}

            Dim Clr As Color = CType(BDR.BorderBrush, SolidColorBrush).Color
            If BDR.BorderThickness.Top Then pdf.DrawLine(New Pen(Clr, BDR.BorderThickness.Top), pts(0), pts(1))
            If BDR.BorderThickness.Right Then pdf.DrawLine(New Pen(Clr, BDR.BorderThickness.Right), pts(1), pts(2))
            If BDR.BorderThickness.Bottom Then pdf.DrawLine(New Pen(Clr, BDR.BorderThickness.Bottom), pts(2), pts(3))
            If BDR.BorderThickness.Left Then pdf.DrawLine(New Pen(Clr, BDR.BorderThickness.Left), pts(3), pts(0))
        ElseIf TypeOf lTB(x) Is Rectangle Then
            Dim Rect As Rectangle = lTB(x)
            Dim ttv As GeneralTransform = Rect.TransformToVisual(myXAMLcontrol)
            Dim ScreenCoords As Point = ttv.TransformPoint(New Point(0, 0))
            Dim pts() As Point = {
                New Point(ScreenCoords.X + Rect.Margin.Left, ScreenCoords.Y + Rect.Margin.Top),
                New Point(ScreenCoords.X + Rect.ActualWidth - Rect.Margin.Right, ScreenCoords.Y + Rect.Margin.Top),
                New Point(ScreenCoords.X + Rect.ActualWidth - Rect.Margin.Right, ScreenCoords.Y + Rect.ActualHeight - Rect.Margin.Bottom),
                New Point(ScreenCoords.X + Rect.Margin.Left, ScreenCoords.Y + Rect.ActualHeight - Rect.Margin.Bottom)}

            Dim MyPen1 As New Pen(CType(Rect.Stroke, SolidColorBrush).Color, Rect.StrokeThickness)
            MyPen1.DashStyle = DashStyle.Custom
            MyPen1.DashPattern = Rect.StrokeDashArray.ToArray
            Dim MyPen2 As New Pen(CType(Rect.Stroke, SolidColorBrush).Color, Rect.StrokeThickness)
            MyPen2.DashStyle = DashStyle.Custom
            MyPen2.DashPattern = Rect.StrokeDashArray.ToArray

            pdf.DrawLine(MyPen2, pts(0), pts(1))
            pdf.DrawLine(MyPen1, pts(1), pts(2))
            pdf.DrawLine(MyPen2, pts(2), pts(3))
            pdf.DrawLine(MyPen1, pts(3), pts(0))
        End If
    Next
    Dim file As StorageFile = Await ThisApp.AppStorageFolder.CreateFileAsync("Temp.PDF", Windows.Storage.CreationCollisionOption.ReplaceExisting)
    Await pdf.SaveAsync(file)
    Return True
End Function

Private Sub FindTextBlocks(uiElement As Object, foundOnes As IList(Of Object))
    If TypeOf uiElement Is TextBlock Then
        Dim uiElementAsTextBlock = DirectCast(uiElement, TextBlock)
        If uiElementAsTextBlock.Visibility = Visibility.Visible Then
            foundOnes.Add(uiElementAsTextBlock)
        End If
    ElseIf TypeOf uiElement Is Panel Then
        Dim uiElementAsCollection = DirectCast(uiElement, Panel)
        If uiElementAsCollection.Visibility = Visibility.Visible Then
            For Each element In uiElementAsCollection.Children
                FindTextBlocks(element, foundOnes)
            Next
        End If
    ElseIf TypeOf uiElement Is UserControl Then
        Dim uiElementAsUserControl = DirectCast(uiElement, UserControl)
        If uiElementAsUserControl.Visibility = Visibility.Visible Then
            FindTextBlocks(uiElementAsUserControl.Content, foundOnes)
        End If
    ElseIf TypeOf uiElement Is ContentControl Then
        Dim uiElementAsContentControl = DirectCast(uiElement, ContentControl)
        If uiElementAsContentControl.Visibility = Visibility.Visible Then
            FindTextBlocks(uiElementAsContentControl.Content, foundOnes)
        End If
    ElseIf TypeOf uiElement Is Border Then
        Dim uiElementAsBorder = DirectCast(uiElement, Border)
        If uiElementAsBorder.Visibility = Visibility.Visible Then
            foundOnes.Add(uiElementAsBorder)
            FindTextBlocks(uiElementAsBorder.Child, foundOnes)
        End If
    ElseIf TypeOf uiElement Is Rectangle Then
        Dim uiElementAsRectangle = DirectCast(uiElement, Rectangle)
        foundOnes.Add(uiElementAsRectangle)
    End If
End Sub

实际结果: