C#解析PDF的方式有很多，比較好用的有ITestSharp和PdfBox。
PDF內容頁如果是圖片類型，例如掃描件，則需要進行OCR（光學字符識別）。
文本內容的PDF文檔，解析的過程中，我目前僅發現能以字符串的形式讀取的，不能夠讀取其中的表格。據說PDF文檔結構中是沒有表格概念的，因此這個自然是讀不到的，如果果真如此，則PDF中表格內容的解析，只能對獲取到的字符串按照一定的邏輯自行解析了。
ITestSharp是一C#開源項目，PdfBox為Java開源項目，借助於IKVM在.Net平台下有實現。
Pdf轉換Image，使用的是GhostScript，可以以API的方式調用，也可以以Windows命令行的方式調用。
OCR使用的是Asprise，識別效果較好（商業），另外還可以使用MS的ImageScaning（2007）或OneNote（2010）（需要依賴Office組件），Tessert（HP->Google）（效果很差）。
附上ITestSharp、PdfBox對PDF的解析代碼。
ITestSharp輔助類
1 using System;
2 using System.Collections.Generic;
3 using System.Text;
4
5 using iTextSharp.text.pdf;
6 using iTextSharp.text.pdf.parser;
7 using System.IO;
8
9 namespace eyuan
10 {
11 public static class ITextSharpHandler
12 {
13 /// <summary>
14 /// 讀取PDF文本內容
15 /// </summary>
16 /// <param name="fileName"></param>
17 /// <returns></returns>
18 public static string ReadPdf(string fileName)
19 {
20 if (!File.Exists(fileName))
21 {
22 LogHandler.LogWrite(@"指定的PDF文件不存在：" + fileName);
23 return string.Empty;
24 }
25 //
26 string fileContent = string.Empty;
27 StringBuilder sbFileContent = new StringBuilder();
28 //打開文件
29 PdfReader reader = null;
30 try
31 {
32 reader = new PdfReader(fileName);
33 }
34 catch (Exception ex)
35 {
36 LogHandler.LogWrite(string.Format(@"加載PDF文件{0}失敗,錯誤:{1}", new string[] { fileName, ex.ToString() }));
37
38 if (reader != null)
39 {
40 reader.Close();
41 reader = null;
42 }
43
44 return string.Empty;
45 }
46
47 try
48 {
49 //循環各頁（索引從1開始）
50 for (int i = 1; i <= reader.NumberOfPages; i++)
51 {
52 sbFileContent.AppendLine(PdfTextExtractor.GetTextFromPage(reader, i));
53
54 }
55
56 }
57 catch (Exception ex)
58 {
59 LogHandler.LogWrite(string.Format(@"解析PDF文件{0}失敗,錯誤:{1}", new string[] { fileName, ex.ToString() }));
60
61 }
62 finally
63 {
64 if (reader != null)
65 {
66 reader.Close();
67 reader = null;
68 }
69 }
70 //
71 fileContent = sbFileContent.ToString();
72 return fileContent;
73 }
74 /// <summary>
75 /// 獲取PDF頁數
76 /// </summary>
77 /// <param name="fileName"></param>
78 /// <returns></returns>
79 public static int GetPdfPageCount(string fileName)
80 {
81 if (!File.Exists(fileName))
82 {
83 LogHandler.LogWrite(@"指定的PDF文件不存在：" + fileName);
84 return -1;
85 }
86 //打開文件
87 PdfReader reader = null;
88 try
89 {
90 reader = new PdfReader(fileName);
91 }
92 catch (Exception ex)
93 {
94 LogHandler.LogWrite(string.Format(@"加載PDF文件{0}失敗,錯誤:{1}", new string[] { fileName, ex.ToString() }));
95
96 if (reader != null)
97 {
98 reader.Close();
99 reader = null;
100 }
101
102 return -1;
103 }
104 //
105 return reader.NumberOfPages;
106 }
107 }
108 }
PDFBox輔助類
1 using org.pdfbox.pdmodel;
2 using org.pdfbox.util;
3 using System;
4 using System.Collections.Generic;
5 using System.IO;
6 using System.Text;
7
8 namespace eyuan
9 {
10 public static class PdfBoxHandler
11 {
12 /// <summary>
13 /// 使用PDFBox組件進行解析
14 /// </summary>
15 /// <param name="input">PDF文件路徑</param>
16 /// <returns>PDF文本內容</returns>
17 public static string ReadPdf(string input)
18 {
19 if (!File.Exists(input))
20 {
21 LogHandler.LogWrite(@"指定的PDF文件不存在：" + input);
22 return null;
23 }
24 else
25 {
26 PDDocument pdfdoc = null;
27 string strPDFText = null;
28 PDFTextStripper stripper = null;
29
30 try
31 {
32 //加載PDF文件
33 pdfdoc = PDDocument.load(input);
34 }
35 catch (Exception ex)
36 {
37 LogHandler.LogWrite(string.Format(@"加載PDF文件{0}失敗,錯誤:{1}", new string[] { input, ex.ToString() }));
38
39 if (pdfdoc != null)
40 {
41 pdfdoc.close();
42 pdfdoc = null;
43 }
44
45 return null;
46 }
47
48 try
49 {
50 //解析PDF文件
51 stripper = new PDFTextStripper();
52 strPDFText = stripper.getText(pdfdoc);
53
54
55
56 }
57 catch (Exception ex)
58 {
59 LogHandler.LogWrite(string.Format(@"解析PDF文件{0}失敗,錯誤:{1}", new string[] { input, ex.ToString() }));
60
61 }
62 finally
63 {
64 if (pdfdoc != null)
65 {
66 pdfdoc.close();
67 pdfdoc = null;
68 }
69 }
70
71 return strPDFText;
72 }
73
74 }
75 }
76 }
另外附上PDF轉Image，然後對Image進行OCR的代碼。
轉換PDF為Jpeg圖片代碼（GhostScript輔助類）
1 using System;
2 using System.Collections;
3 using System.Collections.Generic;
4 using System.Runtime.InteropServices;
5 using System.Text;
6
7 namespace eyuan
8 {
9 public class GhostscriptHandler
10 {
11
12 #region GhostScript Import
13 /// <summary>創建Ghostscript的實例
14 /// This instance is passed to most other gsapi functions.
15 /// The caller_handle will be provided to callback functions.
16 /// At this stage, Ghostscript supports only one instance. </summary>
17 /// <param name="pinstance"></param>
18 /// <param name="caller_handle"></param>
19 /// <returns></returns>
20 [DllImport("gsdll32.dll", EntryPoint = "gsapi_new_instance")]
21 private static extern int gsapi_new_instance(out IntPtr pinstance, IntPtr caller_handle);
22 /// <summary>This is the important function that will perform the conversion
23 ///
24 /// </summary>
25 /// <param name="instance"></param>
26 /// <param name="argc"></param>
27 /// <param name="argv"></param>
28 /// <returns></returns>
29 [DllImport("gsdll32.dll", EntryPoint = "gsapi_init_with_args")]
30 private static extern int gsapi_init_with_args(IntPtr instance, int argc, IntPtr argv);
31 /// <summary>
32 /// Exit the interpreter.
33 /// This must be called on shutdown if gsapi_init_with_args() has been called,
34 /// and just before gsapi_delete_instance().
35 /// 退出
36 /// </summary>
37 /// <param name="instance"></param>
38 /// <returns></returns>
39 [DllImport("gsdll32.dll", EntryPoint = "gsapi_exit")]
40 private static extern int gsapi_exit(IntPtr instance);
41 /// <summary>
42 /// Destroy an instance of Ghostscript.
43 /// Before you call this, Ghostscript must have finished.
44 /// If Ghostscript has been initialised, you must call gsapi_exit before gsapi_delete_instance.
45 /// 銷毀實例
46 /// </summary>
47 /// <param name="instance"></param>
48 [DllImport("gsdll32.dll", EntryPoint = "gsapi_delete_instance")]
49 private static extern void gsapi_delete_instance(IntPtr instance);
50 #endregion
51
52 #region 變量
53 private string _sDeviceFormat;
54 private int _iWidth;
55 private int _iHeight;
56 private int _iResolutionX;
57 private int _iResolutionY;
58 private int _iJPEGQuality;
59 private Boolean _bFitPage;
60 private IntPtr _objHandle;
61 #endregion
62
63 #region 屬性
64 /// <summary>
65 /// 輸出格式
66 /// </summary>
67 public string OutputFormat
68 {
69 get { return _sDeviceFormat; }
70 set { _sDeviceFormat = value; }
71 }
72 /// <summary>
73 ///
74 /// </summary>
75 public int Width
76 {
77 get { return _iWidth; }
78 set { _iWidth = value; }
79 }
80 /// <summary>
81 ///
82 /// </summary>
83 public int Height
84 {
85 get { return _iHeight; }
86 set { _iHeight = value; }
87 }
88 /// <summary>
89 ///
90 /// </summary>
91 public int ResolutionX
92 {
93 get { return _iResolutionX; }
94 set { _iResolutionX = value; }
95 }
96 /// <summary>
97 ///
98 /// </summary>
99 public int ResolutionY
100 {
101 get { return _iResolutionY; }
102 set { _iResolutionY = value; }
103 }
104 /// <summary>
105 ///
106 /// </summary>
107 public Boolean FitPage
108 {
109 get { return _bFitPage; }
110 set { _bFitPage = value; }
111 }
112 /// <summary>Quality of compression of JPG
113 /// Jpeg文檔質量
114 /// </summary>
115 public int JPEGQuality
116 {
117 get { return _iJPEGQuality; }
118 set { _iJPEGQuality = value; }
119 }
120 #endregion
121
122 #region 初始化（實例化對象）
123 /// <summary>
124 ///
125 /// </summary>
126 /// <param name="objHandle"></param>
127 public GhostscriptHandler(IntPtr objHandle)
128 {
129 _objHandle = objHandle;
130 }
131 public GhostscriptHandler()
132 {
133 _objHandle = IntPtr.Zero;
134 }
135 #endregion
136
137 #region 字符串處理
138 /// <summary>
139 /// 轉換Unicode字符串到Ansi字符串
140 /// </summary>
141 /// <param name="str">Unicode字符串</param>
142 /// <returns>Ansi字符串（字節數組格式）</returns>
143 private byte[] StringToAnsiZ(string str)
144 {
145 //' Convert a Unicode string to a null terminated Ansi string for Ghostscript.
146 //' The result is stored in a byte array. Later you will need to convert
147 //' this byte array to a pointer with GCHandle.Alloc(XXXX, GCHandleType.Pinned)
148 //' and GSHandle.AddrOfPinnedObject()
149 int intElementCount;
150 int intCounter;
151 byte[] aAnsi;
152 byte bChar;
153 intElementCount = str.Length;
154 aAnsi = new byte[intElementCount + 1];
155 for (intCounter = 0; intCounter < intElementCount; intCounter++)
156 {
157 bChar = (byte)str[intCounter];
158 aAnsi[intCounter] = bChar;
159 }
160 aAnsi[intElementCount] = 0;
161 return aAnsi;
162 }
163 #endregion
164
165 #region 轉換文件
166 /// <summary>
167 /// 轉換文件
168 /// </summary>
169 /// <param name="inputFile">輸入的PDF文件路徑</param>
170 /// <param name="outputFile">輸出的Jpeg圖片路徑</param>
171 /// <param name="firstPage">第一頁</param>
172 /// <param name="lastPage">最後一頁</param>
173 /// <param name="deviceFormat">格式（文件格式）</param>
174 /// <param name="width">寬度</param>
175 /// <param name="height">高度</param>
176 public void Convert(string inputFile, string outputFile,
177 int firstPage, int lastPage, string deviceFormat, int width, int height)
178 {
179 //判斷文件是否存在
180 if (!System.IO.File.Exists(inputFile))
181 {
182 LogHandler.LogWrite(string.Format("文件{0}不存在", inputFile));
183 return;
184 }
185 int intReturn;
186 IntPtr intGSInstanceHandle;
187 object[] aAnsiArgs;
188 IntPtr[] aPtrArgs;
189 GCHandle[] aGCHandle;
190 int intCounter;
191 int intElementCount;
192 IntPtr callerHandle;
193 GCHandle gchandleArgs;
194 IntPtr intptrArgs;
195 string[] sArgs = GetGeneratedArgs(inputFile, outputFile,
196 firstPage, lastPage, deviceFormat, width, height);
197 // Convert the Unicode strings to null terminated ANSI byte arrays
198 // then get pointers to the byte arrays.
199 intElementCount = sArgs.Length;
200 aAnsiArgs = new object[intElementCount];
201 aPtrArgs = new IntPtr[intElementCount];
202 aGCHandle = new GCHandle[intElementCount];
203 // Create a handle for each of the arguments after
204 // they've been converted to an ANSI null terminated
205 // string. Then store the pointers for each of the handles
206 for (intCounter = 0; intCounter < intElementCount; intCounter++)
207 {
208 aAnsiArgs[intCounter] = StringToAnsiZ(sArgs[intCounter]);
209 aGCHandle[intCounter] = GCHandle.Alloc(aAnsiArgs[intCounter], GCHandleType.Pinned);
210 aPtrArgs[intCounter] = aGCHandle[intCounter].AddrOfPinnedObject();
211 }
212 // Get a new handle for the array of argument pointers
213 gchandleArgs = GCHandle.Alloc(aPtrArgs, GCHandleType.Pinned);
214 intptrArgs = gchandleArgs.AddrOfPinnedObject();
215 intReturn = gsapi_new_instance(out intGSInstanceHandle, _objHandle);
216 callerHandle = IntPtr.Zero;
217 try
218 {
219 intReturn = gsapi_init_with_args(intGSInstanceHandle, intElementCount, intptrArgs);
220 }
221 catch (Exception ex)
222 {
223 LogHandler.LogWrite(string.Format("PDF文件{0}轉換失敗.\n錯誤:{1}",new string[]{inputFile,ex.ToString()}));
224
225 }
226 finally
227 {
228 for (intCounter = 0; intCounter < intReturn; intCounter++)
229 {
230 aGCHandle[intCounter].Free();
231 }
232 gchandleArgs.Free();
233 gsapi_exit(intGSInstanceHandle);
234 gsapi_delete_instance(intGSInstanceHandle);
235 }
236 }
237 #endregion
238
239 #region 轉換文件
240 /// <summary>
241 ///
242 /// </summary>
243 /// <param name="inputFile"></param>
244 /// <param name="outputFile"></param>
245 /// <param name="firstPage"></param>
246 /// <param name="lastPage"></param>
247 /// <param name="deviceFormat"></param>
248 /// <param name="width"></param>
249 /// <param name="height"></param>
250 /// <returns></returns>
251 private string[] GetGeneratedArgs(string inputFile, string outputFile,
252 int firstPage, int lastPage, string deviceFormat, int width, int height)
253 {
254 this._sDeviceFormat = deviceFormat;
255 this._iResolutionX = width;
256 this._iResolutionY = height;
257 // Count how many extra args are need - HRangel - 11/29/2006, 3:13:43 PM
258 ArrayList lstExtraArgs = new ArrayList();
259 if (_sDeviceFormat == "jpg" && _iJPEGQuality > 0 && _iJPEGQuality < 101)
260 lstExtraArgs.Add("-dJPEGQ=" + _iJPEGQuality);
261 if (_iWidth > 0 && _iHeight > 0)
262 lstExtraArgs.Add("-g" + _iWidth + "x" + _iHeight);
263 if (_bFitPage)
264 lstExtraArgs.Add("-dPDFFitPage");
265 if (_iResolutionX > 0)
266 {
267 if (_iResolutionY > 0)
268 lstExtraArgs.Add("-r" + _iResolutionX + "x" + _iResolutionY);
269 else
270 lstExtraArgs.Add("-r" + _iResolutionX);
271 }
272 // Load Fixed Args - HRangel - 11/29/2006, 3:34:02 PM
273 int iFixedCount = 17;
274 int iExtraArgsCount = lstExtraArgs.Count;
275 string[] args = new string[iFixedCount + lstExtraArgs.Count];
276 /*
277 // Keep gs from writing information to standard output
278 "-q",
279 "-dQUIET",
280
281 "-dPARANOIDSAFER", // Run this command in safe mode
282 "-dBATCH", // Keep gs from going into interactive mode
283 "-dNOPAUSE", // Do not prompt and pause for each page
284 "-dNOPROMPT", // Disable prompts for user interaction
285 "-dMaxBitmap=500000000", // Set high for better performance
286
287 // Set the starting and ending pages
288 String.Format("-dFirstPage={0}", firstPage),
289 String.Format("-dLastPage={0}", lastPage),
290
291 // Configure the output anti-aliasing, resolution, etc
292 "-dAlignToPixels=0",
293 "-dGridFitTT=0",
294 "-sDEVICE=jpeg",
295 "-dTextAlphaBits=4",
296 "-dGraphicsAlphaBits=4",
297 */
298 args[0] = "pdf2img";//this parameter have little real use
299 args[1] = "-dNOPAUSE";//I don't want interruptions
300 args[2] = "-dBATCH";//stop after
301 //args[3]="-dSAFER";
302 args[3] = "-dPARANOIDSAFER";
303 args[4] = "-sDEVICE=" + _sDeviceFormat;//what kind of export format i should provide
304 args[5] = "-q";
305 args[6] = "-dQUIET";
306 args[7] = "-dNOPROMPT";
307 args[8] = "-dMaxBitmap=500000000";
308 args[9] = String.Format("-dFirstPage={0}", firstPage);
309 args[10] = String.Format("-dLastPage={0}", lastPage);
310 args[11] = "-dAlignToPixels=0";
311 args[12] = "-dGridFitTT=0";
312 args[13] = "-dTextAlphaBits=4";
313 args[14] = "-dGraphicsAlphaBits=4";
314 //For a complete list watch here:
315 //http://pages.cs.wisc.edu/~ghost/doc/cvs/Devices.htm
316 //Fill the remaining parameters
317 for (int i = 0; i < iExtraArgsCount; i++)
318 {
319 args[15 + i] = (string)lstExtraArgs[i];
320 }
321 //Fill outputfile and inputfile
322 args[15 + iExtraArgsCount] = string.Format("-sOutputFile={0}", outputFile);
323 args[16 + iExtraArgsCount] = string.Format("{0}", inputFile);
324 return args;
325 }
326 #endregion
327
328
329 }
330 }
OCR，識別Image代碼（AsPrise輔助類）
1 using System;
2 using System.Collections.Generic;
3 using System.Runtime.InteropServices;
4 using System.Text;
5
6 namespace PDFCaptureService
7 {
8 public static class AspriseOCRHandler
9 {
10 #region 外部引用
11 [DllImport("AspriseOCR.dll", EntryPoint = "OCR", CallingConvention = CallingConvention.Cdecl)]
12 public static extern IntPtr OCR(string file, int type);
13 [DllImport("AspriseOCR.dll", EntryPoint = "OCRpart", CallingConvention = CallingConvention.Cdecl)]
14 static extern IntPtr OCRpart(string file, int type, int startX, int
15 startY, int width, int height);
16 [DllImport("AspriseOCR.dll", EntryPoint = "OCRBarCodes", CallingConvention = CallingConvention.Cdecl)]
17 static extern IntPtr OCRBarCodes(string file, int type);
18 [DllImport("AspriseOCR.dll", EntryPoint = "OCRpartBarCodes", CallingConvention = CallingConvention.Cdecl)]
19 static extern IntPtr OCRpartBarCodes(string file, int type, int
20 startX, int startY, int width, int height);
21 #endregion
22
23 /// <summary>
24 ///
25 /// </summary>
26 /// <param name="fileName"></param>
27 /// <returns></returns>
28 public static string ReadImage(string fileName)
29 {
30 IntPtr ptrFileContent = OCR(fileName, -1);
31 string fileContent = Marshal.PtrToStringAnsi(ptrFileContent);
32 //
33 return fileContent;
34 }
35 }
36 }
調用示例
1 GhostscriptHandler ghostscriptHandler = new GhostscriptHandler(); 2 string tempJpgFileName = string.Format(GhostScriptImageName, Guid.NewGuid().ToString()); 3 int pdfPageCount = ITextSharpHandler.GetPdfPageCount(fileName); 4 ghostscriptHandler.Convert(fileName, tempJpgFileName, 1, pdfPageCount, "jpeg", 100, 100); 5 fileContent = AspriseOCRHandler.ReadImage(fileName);
