.net - 如何在打印前预处理PrintDocument以计算总页数？

Question

回答这个问题...

Printing page x of y in .Net

已接受的答案包括此声明...

You don't have to print it twice, you just have to simulate printing the first time.

那么，如何才能先一次性浏览文档而不将任何输出发送到打印机或屏幕？

Answer 1

您将需要创建打印机设备上下文并使用该设备上下文作为引用 DC 来渲染页面，同时跟踪已渲染的页面数。这必须在 .NET 打印基础设施的范围之外完成。

1. 获取引用打印机 DC
2. 根据引用打印机 DC 创建位图
3. 创建 Graphics 对象以在位图上绘制
4. 使用图形对象将页面渲染为位图(在此处计算页面数)
5. 需要打印更多数据？转到4

这是第 1 步的一个例子，假设您正在 winforms 中工作...

 Private Function GetHighResolutionGraphics() As Graphics

        Try

            Dim HighestResolution As Printing.PrinterResolution = Nothing
            Dim HighestResolutionPrinter As String = ""
            Dim XResolution As Integer = Integer.MinValue

            Using dlg As New PrintDialog

                For Each Printer As String In Printing.PrinterSettings.InstalledPrinters
                    dlg.PrinterSettings.PrinterName = Printer
                    For Each Resolution As Printing.PrinterResolution In dlg.PrinterSettings.PrinterResolutions
                        Using gr As Graphics = dlg.PrinterSettings.CreateMeasurementGraphics()
                            If gr.DpiX > XResolution Then
                                HighestResolution = Resolution
                                HighestResolutionPrinter = Printer
                                XResolution = gr.DpiX
                            End If
                        End Using
                    Next
                Next

                dlg.PrinterSettings.PrinterName = HighestResolutionPrinter
                dlg.PrinterSettings.DefaultPageSettings.PrinterResolution = HighestResolution

                Return dlg.PrinterSettings.CreateMeasurementGraphics()

            End Using

        Catch ex As Exception
            ' handle or ignore .NET AccessViolation for certain network printers that are turned off, etc...
        End Try

        Return Me.CreateGraphics()

    End Function

第 2 步“简单地”使用返回的引用图形对象和已实现的 PagePrint 事件代码将页面渲染为适当的位图，同时跟踪正在渲染的页面数。不要忘记将 PagePrint 事件重构为接受 Graphics 对象的单独例程，以便它可用于打印、预览和页码编号。不要忘记处理 Graphics 对象和 Bitmap

using gfxReference as Graphics = GetHighResolutionGraphics()
  using bmpPage as new Bitmap(gfxReference.DpiX * 8.5, gfxReference.DpiY * 11)
    using gfxRender as Graphics = Graphics.FromImage(bmpPage)
      gfxRender.Clear(Color.White)
      // Existing PagePrint event logic goes here (uses gfxRender)
      // Track Number of pages printed
    end using
  end using
end using