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将 RTF 文件转换为 PDF：开发人员指南

· PDF 编程

将 RTF 文件转换为 PDF：Delphi、C# 和 VB.Net 开发人员指南。

在文档处理领域，将 Rich Text Format (RTF) 文件转换为 Portable Document Format (PDF) 是一项常见的任务。 这种转换可确保文档在不同平台上的布局保持一致。 本指南提供了使用我们的 PDF 开发库在 Delphi、C# 和 VB.Net 中进行高效 RTF 到 PDF 转换的详细解决方案。 PDF 开发库 在 Delphi、C# 和 VB.Net 中。 遵循本指南，您可以无缝地将 RTF 文件转换为 PDF 文档，同时保持与原始内容的高度一致性。 让我们逐步了解此过程。

问题描述

这里的主要挑战是将 RTF 文件转换为 PDF 文件，同时确保原始文档的格式和布局得到保留。 这涉及：

  1. 加载 RTF 文件。
  2. 设置用于渲染的虚拟设备上下文。
  3. 将 RTF 内容打印到虚拟设备上下文。
  4. 将渲染后的内容保存为 PDF 文件。

实现目标的步骤。

  1. 初始化环境：
    • 加载 losLab PDF 库。
    • 将 RTF 文件加载到富文本控件中。
  2. 设置设备上下文：
    • 创建一个虚拟设备上下文，该上下文模拟 A4 页面的尺寸。
    • 计算所需的缩放比例，以使内容适应 PDF 页面的大小。
  3. 处理 RTF 内容：
    • 使用虚拟设备上下文来格式化和打印 RTF 内容。
    • 捕获打印的内容，并从中创建一个新的 PDF 页面。
  4. 保存 PDF 文档：
    • 将生成的 PDF 页面保存到磁盘。
    • 通过循环遍历 RTF 内容，并在需要时创建新的 PDF 文档，来处理多个页面。

Delphi 代码示例。

以下是使用我们的 PDF 库将 RTF 文件转换为 PDF 文件的 Delphi 实现示例。
以下代码使用 PDF 开发库的 DLL 版本（Delphi 也有可用的 Pascal 源代码版本）。

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unit MainUnit;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, PDFlibAX_TLB, ActiveX;
 
type
  TForm1 = class(TForm)
    RichEdit1: TRichEdit;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    function PrintRtfBox(hDc: HDC; rtfBox: TRichEdit; FirstChar: Integer): Integer;
  public
  end;
 
var
  Form1: TForm1;
  PdfDoc: TPDFLibrary;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.FormCreate(Sender: TObject);
begin
  PdfDoc := TPDFLibrary.Create(Self);
  RichEdit1.Width := Round(ScaleX(210, mmPixel));
  RichEdit1.Height := Round(ScaleY(297, mmPixel));
  RichEdit1.Lines.LoadFromFile(ExtractFilePath(Application.ExeName) + 'Test.rtf');
end;
 
procedure TForm1.Button1Click(Sender: TObject);
var
  Dc: HDC;
  PageNumber, LastChar, PdfDocId: Integer;
begin
  PageNumber := 1;
  LastChar := 0;
  repeat
    Dc := PdfDoc.GetCanvasDC(Round(ScaleX(210, mmPixel)), Round(ScaleY(297, mmPixel)));
    LastChar := PrintRtfBox(Dc, RichEdit1, LastChar);
    PdfDoc.LoadFromCanvasDc(96, 0);
    PdfDocId := PdfDoc.SelectedPdfDocument;
    PdfDoc.SaveToFile(ExtractFilePath(Application.ExeName) + 'Test' + IntToStr(PageNumber) + '.pdf');
    PdfDoc.RemovePdfDocument(PdfDocId);
    Inc(PageNumber);
  until LastChar = 0;
  ShowMessage('Done');
end;
 
function TForm1.PrintRtfBox(hDc: HDC; rtfBox: TRichEdit; FirstChar: Integer): Integer;
var
  RcDrawTo, RcPage: TRect;
  Fr: TFormatRange;
  NextCharPosition: Integer;
begin
  RcPage.Left := 0;
  RcPage.Right := rtfBox.Left + rtfBox.Width + 100;
  RcPage.Top := 0;
  RcPage.Bottom := rtfBox.Top + rtfBox.Height + 100;
  RcDrawTo.Left := rtfBox.Left;
  RcDrawTo.Top := rtfBox.Top;
  RcDrawTo.Right := rtfBox.Left + rtfBox.Width;
  RcDrawTo.Bottom := rtfBox.Top + rtfBox.Height;
 
  Fr.hdc := hDc;
  Fr.hdcTarget := hDc;
  Fr.rc := RcDrawTo;
  Fr.rcPage := RcPage;
  Fr.chrg.cpMin := FirstChar;
  Fr.chrg.cpMax := -1;
 
  NextCharPosition := SendMessage(rtfBox.Handle, EM_FORMATRANGE, 1, LPARAM(@Fr));
  if NextCharPosition < Length(rtfBox.Text) then
    Result := NextCharPosition
  else
    Result := 0;
end;
 
end.

C# 代码示例

以下是 C# 实现，它实现了与 Delphi 示例相同的功能。

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using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using PDFLibrary;
 
namespace RtfToPdf
{
    public partial class Form1 : Form
    {
        private PDFLibrary PdfDoc;
 
        [StructLayout(LayoutKind.Sequential)]
        private struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }
 
        [StructLayout(LayoutKind.Sequential)]
        private struct CharRange
        {
            public int cpMin;
            public int cpMax;
        }
 
        [StructLayout(LayoutKind.Sequential)]
        private struct FormatRange
        {
            public IntPtr hDc;
            public IntPtr hdcTarget;
            public RECT rc;
            public RECT RcPage;
            public CharRange chrg;
        }
 
        private const int WM_USER = 0x400;
        private const int EM_FORMATRANGE = WM_USER + 57;
 
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, ref FormatRange lParam);
 
        public Form1()
        {
            InitializeComponent();
            PdfDoc = new PDFLibrary();
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
            richTextBox1.SetBounds(0, 0, Convert.ToInt32(ScaleX(210, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)), Convert.ToInt32(ScaleY(297, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)));
            richTextBox1.LoadFile(Application.StartupPath + "\\Test.rtf");
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            IntPtr Dc;
            int PageNumber = 1;
            int LastChar = 0;
            int PdfDocId;
            do
            {
                Dc = PdfDoc.GetCanvasDC(Convert.ToInt32(ScaleX(210, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)), Convert.ToInt32(ScaleY(297, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)));
                LastChar = PrintRtfBox(Dc, richTextBox1, LastChar);
                PdfDoc.LoadFromCanvasDc(96, 0);
                PdfDocId = PdfDoc.SelectedPdfDocument;
                PdfDoc.SaveToFile(Application.StartupPath + "\\Test" + PageNumber + ".pdf");
                PdfDoc.RemovePdfDocument(PdfDocId);
                PageNumber++;
            } while (LastChar != 0);
            MessageBox.Show("Done");
        }
 
        private int PrintRtfBox(IntPtr hDc, RichTextBox rtfBox, int FirstChar)
        {
            RECT RcDrawTo = new RECT();
            RECT RcPage = new RECT();
            FormatRange Fr = new FormatRange();
 
            RcPage.Left = 0;
            RcPage.Right = rtfBox.Left + rtfBox.Width + 100;
            RcPage.Top = 0;
            RcPage.Bottom = rtfBox.Top + rtfBox.Height + 100;
            RcDrawTo.Left = rtfBox.Left;
            RcDrawTo.Top = rtfBox.Top;
            RcDrawTo.Right = rtfBox.Left + rtfBox.Width;
            RcDrawTo.Bottom = rtfBox.Top + rtfBox.Height;
 
            Fr.hDc = hDc;
            Fr.hdcTarget = hDc;
            Fr.rc = RcDrawTo;
            Fr.RcPage = RcPage;
            Fr.chrg.cpMin = FirstChar;
            Fr.chrg.cpMax = -1;
 
            IntPtr wParam = new IntPtr(1);
            IntPtr NextCharPosition = SendMessage(rtfBox.Handle, EM_FORMATRANGE, wParam, ref Fr);
 
            if (NextCharPosition.ToInt32() < rtfBox.Text.Length)
                return NextCharPosition.ToInt32();
            else
                return 0;
        }
 
        private float ScaleX(float value, GraphicsUnit fromUnit, GraphicsUnit toUnit)
        {
            using (Graphics g = this.CreateGraphics())
            {
                return value * g.DpiX / 96.0f;
            }
        }
 
        private float ScaleY(float value, GraphicsUnit fromUnit, GraphicsUnit toUnit)
        {
            using (Graphics g = this.CreateGraphics())
            {
                return value * g.DpiY / 96.0f;
            }
        }
    }
}

说明和理由

  • 初始化： Delphi 和 C# 版本都初始化了 losLab PDF Library） DLL 版本。RTF 文件加载到富文本控件中（Delphi 中的 RichEdit 和 C# 中的 RichTextBox）。
  • 设备上下文设置： 设备上下文被设置为模拟 A4 页面大小，以确保内容在渲染时能够正确地适应。
  • 内容处理： 好的。 PrintRtfBox 函数（或方法）格式化 RTF 内容并将其打印到设备上下文中。该方法计算所需的尺寸，并调用适当的 Windows API 来处理文本格式。
  • PDF 生成： 在两个示例中的循环中，RTF 内容按页面逐页处理，并在必要时创建新的 PDF 文档。每个页面都保存到磁盘，然后从内存中删除，以高效地管理资源。
  • 完成通知： 在处理完所有页面后，一个消息框会通知用户转换已完成。

遵循这些步骤，我们可以确保可靠且准确地将 RTF 文件转换为 PDF 文档，并利用 losLab PDF Library 的功能。这种方法可确保保留原始格式和布局，从而生成高质量的 PDF 输出。

VisualBasic.Net RTF 转 PDF 示例

此外，我们还提供了一个 VB.Net 实现，它具有与 Delphi 和 C# 示例相同的 functionality。

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Imports System.Runtime.InteropServices
Imports PDFlibDLL
 
Public Class Form1
 
    Private PdfDoc As PDFlibrary
 
    <StructLayout(LayoutKind.Sequential)>
    Private Structure RECT
        Public Left As Integer
        Public Top As Integer
        Public Right As Integer
        Public Bottom As Integer
    End Structure
 
    <StructLayout(LayoutKind.Sequential)>
    Private Structure CharRange
        Public cpMin As Integer
        Public cpMax As Integer
    End Structure
 
    <StructLayout(LayoutKind.Sequential)>
    Private Structure FormatRange
        Public hDc As IntPtr
        Public hdcTarget As IntPtr
        Public rc As RECT
        Public rcPage As RECT
        Public chrg As CharRange
    End Structure
 
    Private Const WM_USER As Integer = &H400
    Private Const EM_FORMATRANGE As Integer = WM_USER + 57
 
    <DllImport("user32.dll", CharSet:=CharSet.Auto)>
    Private Shared Function SendMessage(hWnd As IntPtr, wMsg As Integer, wParam As IntPtr, ByRef lParam As FormatRange) As IntPtr
    End Function
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        PdfDoc = New PDFlibrary()
        RichTextBox1.SetBounds(0, 0, Convert.ToInt32(ScaleX(210, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)), Convert.ToInt32(ScaleY(297, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)))
        RichTextBox1.LoadFile(Application.StartupPath & "\Test.rtf")
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim Dc As IntPtr
        Dim PageNumber As Integer = 1
        Dim LastChar As Integer = 0
        Dim PdfDocId As Integer
 
        Do
            Dc = PdfDoc.GetCanvasDC(Convert.ToInt32(ScaleX(210, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)), Convert.ToInt32(ScaleY(297, GraphicsUnit.Millimeter, GraphicsUnit.Pixel)))
            LastChar = PrintRtfBox(Dc, RichTextBox1, LastChar)
            PdfDoc.LoadFromCanvasDc(96, 0)
            PdfDocId = PdfDoc.SelectedPdfDocument
            PdfDoc.SaveToFile(Application.StartupPath & "\Test" & PageNumber & ".pdf")
            PdfDoc.RemovePdfDocument(PdfDocId)
            PageNumber += 1
        Loop While LastChar <> 0
 
        MessageBox.Show("Done")
    End Sub
 
    Private Function PrintRtfBox(hDc As IntPtr, rtfBox As RichTextBox, FirstChar As Integer) As Integer
        Dim RcDrawTo As New RECT()
        Dim RcPage As New RECT()
        Dim Fr As New FormatRange()
 
        RcPage.Left = 0
        RcPage.Right = rtfBox.Left + rtfBox.Width + 100
        RcPage.Top = 0
        RcPage.Bottom = rtfBox.Top + rtfBox.Height + 100
        RcDrawTo.Left = rtfBox.Left
        RcDrawTo.Top = rtfBox.Top
        RcDrawTo.Right = rtfBox.Left + rtfBox.Width
        RcDrawTo.Bottom = rtfBox.Top + rtfBox.Height
 
        Fr.hDc = hDc
        Fr.hdcTarget = hDc
        Fr.rc = RcDrawTo
        Fr.rcPage = RcPage
        Fr.chrg.cpMin = FirstChar
        Fr.chrg.cpMax = -1
 
        Dim wParam As IntPtr = New IntPtr(1)
        Dim NextCharPosition As IntPtr = SendMessage(rtfBox.Handle, EM_FORMATRANGE, wParam, Fr)
 
        If NextCharPosition.ToInt32() < rtfBox.Text.Length Then
            Return NextCharPosition.ToInt32()
        Else
            Return 0
        End If
    End Function
 
    Private Function ScaleX(value As Single, fromUnit As GraphicsUnit, toUnit As GraphicsUnit) As Single
        Using g As Graphics = Me.CreateGraphics()
            Return value * g.DpiX / 96.0F
        End Using
    End Function
 
    Private Function ScaleY(value As Single, fromUnit As GraphicsUnit, toUnit As GraphicsUnit) As Single
        Using g As Graphics = Me.CreateGraphics()
            Return value * g.DpiY / 96.0F
        End Using
    End Function
 
End Class