C#解析PDF

C#解析PDF的方式有很多，比较好用的有ITestSharp和PdfBox。

PDF内容页如果是图片类型，例如扫描件，则需要进行OCR（光学字符识别）。

文本内容的PDF文档，解析的过程中，我目前仅发现能以字符串的形式读取的，不能够读取其中的表格。据说PDF文档结构中是没有表格概念的，因此这个自然是读不到的，如果果真如此，则PDF中表格内容的解析，只能对获取到的字符串按照一定的逻辑自行解析了。

ITestSharp是一C#开源项目，PdfBox为Java开源项目，借助于IKVM在.Net平台下有实现。

Pdf转换Image，使用的是GhostScript，可以以API的方式调用，也可以以Windows命令行的方式调用。

OCR使用的是Asprise，识别效果较好（商业），另外还可以使用MS的ImageScaning（2007）或OneNote（2010）（需要依赖Office组件），Tessert（HP->Google）（效果很差）。

附上ITestSharp、PdfBox对PDF的解析代码。

ITestSharp辅助类

using System;
using System.Collections.Generic;
using System.Text;

using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;
using System.IO;

namespace eyuan
{
    public static class ITextSharpHandler
    {
        /// <summary>
        /// 读取PDF文本内容
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string ReadPdf(string fileName)
        {
            if (!File.Exists(fileName))
            {
                LogHandler.LogWrite(@"指定的PDF文件不存在：" + fileName);
                return string.Empty;
            }
            //
            string fileContent = string.Empty;
            StringBuilder sbFileContent = new StringBuilder();
            //打开文件
            PdfReader reader = null;
            try
            {
                reader = new PdfReader(fileName);
            }
            catch (Exception ex)
            {
                LogHandler.LogWrite(string.Format(@"加载PDF文件{0}失败,错误:{1}", new string[] { fileName, ex.ToString() }));

                if (reader != null)
                {
                    reader.Close();
                    reader = null;
                }

                return string.Empty;
            }

            try
            {
                //循环各页（索引从1开始）
                for (int i = 1; i <= reader.NumberOfPages; i++)
                {
                    sbFileContent.AppendLine(PdfTextExtractor.GetTextFromPage(reader, i));

                }

            }
            catch (Exception ex)
            {
                LogHandler.LogWrite(string.Format(@"解析PDF文件{0}失败,错误:{1}", new string[] { fileName, ex.ToString() }));

            }
            finally
            {
                if (reader != null)
                {
                    reader.Close();
                    reader = null;
                }
            }
            //
            fileContent = sbFileContent.ToString();
            return fileContent;
        }
        /// <summary>
        /// 获取PDF页数
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static int GetPdfPageCount(string fileName)
        {
            if (!File.Exists(fileName))
            {
                LogHandler.LogWrite(@"指定的PDF文件不存在：" + fileName);
                return -1;
            }
            //打开文件
            PdfReader reader = null;
            try
            {
                reader = new PdfReader(fileName);
            }
            catch (Exception ex)
            {
                LogHandler.LogWrite(string.Format(@"加载PDF文件{0}失败,错误:{1}", new string[] { fileName, ex.ToString() }));

                if (reader != null)
                {
                    reader.Close();
                    reader = null;
                }

                return -1;
            }
            //
            return reader.NumberOfPages;
        }
    }
}

 PDFBox辅助类

using org.pdfbox.pdmodel;
using org.pdfbox.util;
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace eyuan
{
    public static class PdfBoxHandler
    {
        /// <summary>
        /// 使用PDFBox组件进行解析
        /// </summary>
        /// <param name="input">PDF文件路径</param>
        /// <returns>PDF文本内容</returns>
        public static string ReadPdf(string input)
        {
            if (!File.Exists(input))
            {
                LogHandler.LogWrite(@"指定的PDF文件不存在：" + input);
                return null;
            }
            else
            {
                PDDocument pdfdoc = null;
                string strPDFText = null;
                PDFTextStripper stripper = null;

                try
                {
                    //加载PDF文件
                    pdfdoc = PDDocument.load(input);
                }
                catch (Exception ex)
                {
                    LogHandler.LogWrite(string.Format(@"加载PDF文件{0}失败,错误:{1}", new string[] { input, ex.ToString() }));

                    if (pdfdoc != null)
                    {
                        pdfdoc.close();
                        pdfdoc = null;
                    }

                    return null;
                }

                try
                {
                    //解析PDF文件
                    stripper = new PDFTextStripper();
                    strPDFText = stripper.getText(pdfdoc);

                   

                }
                catch (Exception ex)
                {
                    LogHandler.LogWrite(string.Format(@"解析PDF文件{0}失败,错误:{1}", new string[] { input, ex.ToString() }));

                }
                finally
                {
                    if (pdfdoc != null)
                    {
                        pdfdoc.close();
                        pdfdoc = null;
                    }
                }

                return strPDFText;
            }

        }
    }
}

另外附上PDF转Image，然后对Image进行OCR的代码。

转换PDF为Jpeg图片代码（GhostScript辅助类）

using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;

namespace eyuan
{
    public class GhostscriptHandler
    {

        #region GhostScript Import
        /// <summary>创建Ghostscript的实例
        /// This instance is passed to most other gsapi functions. 
        /// The caller_handle will be provided to callback functions.  
        ///  At this stage, Ghostscript supports only one instance. </summary>  
        /// <param name="pinstance"></param>  
        /// <param name="caller_handle"></param>  
        /// <returns></returns>   
        [DllImport("gsdll32.dll", EntryPoint = "gsapi_new_instance")]
        private static extern int gsapi_new_instance(out IntPtr pinstance, IntPtr caller_handle);
        /// <summary>This is the important function that will perform the conversion
        /// 
        /// </summary>  
        /// <param name="instance"></param>  
        /// <param name="argc"></param>  
        /// <param name="argv"></param>  
        /// <returns></returns>  
        [DllImport("gsdll32.dll", EntryPoint = "gsapi_init_with_args")]
        private static extern int gsapi_init_with_args(IntPtr instance, int argc, IntPtr argv);
        /// <summary>  
        /// Exit the interpreter. 
        /// This must be called on shutdown if gsapi_init_with_args() has been called, 
        /// and just before gsapi_delete_instance().
        /// 退出
        /// </summary>  
        /// <param name="instance"></param>  
        /// <returns></returns>  
        [DllImport("gsdll32.dll", EntryPoint = "gsapi_exit")]
        private static extern int gsapi_exit(IntPtr instance);
        /// <summary>  
        /// Destroy an instance of Ghostscript. 
        /// Before you call this, Ghostscript must have finished. 
        /// If Ghostscript has been initialised, you must call gsapi_exit before gsapi_delete_instance.   
        /// 销毁实例
        /// </summary>  
        /// <param name="instance"></param>  
        [DllImport("gsdll32.dll", EntryPoint = "gsapi_delete_instance")]
        private static extern void gsapi_delete_instance(IntPtr instance);
        #endregion

        #region 变量
        private string _sDeviceFormat;
        private int _iWidth;
        private int _iHeight;
        private int _iResolutionX;
        private int _iResolutionY;
        private int _iJPEGQuality;
        private Boolean _bFitPage;
        private IntPtr _objHandle;
        #endregion

        #region 属性
        /// <summary>
        /// 输出格式
        /// </summary>
        public string OutputFormat
        {
            get { return _sDeviceFormat; }
            set { _sDeviceFormat = value; }
        }
        /// <summary>
        /// 
        /// </summary>
        public int Width
        {
            get { return _iWidth; }
            set { _iWidth = value; }
        }
        /// <summary>
        /// 
        /// </summary>
        public int Height
        {
            get { return _iHeight; }
            set { _iHeight = value; }
        }
        /// <summary>
        /// 
        /// </summary>
        public int ResolutionX
        {
            get { return _iResolutionX; }
            set { _iResolutionX = value; }
        }
        /// <summary>
        /// 
        /// </summary>
        public int ResolutionY
        {
            get { return _iResolutionY; }
            set { _iResolutionY = value; }
        }
        /// <summary>
        /// 
        /// </summary>
        public Boolean FitPage
        {
            get { return _bFitPage; }
            set { _bFitPage = value; }
        }
        /// <summary>Quality of compression of JPG
        /// Jpeg文档质量
        /// </summary>  
        public int JPEGQuality
        {
            get { return _iJPEGQuality; }
            set { _iJPEGQuality = value; }
        }
        #endregion

        #region 初始化（实例化对象）
        /// <summary>
        /// 
        /// </summary>
        /// <param name="objHandle"></param>
        public GhostscriptHandler(IntPtr objHandle)
        {
            _objHandle = objHandle;
        }
        public GhostscriptHandler()
        {
            _objHandle = IntPtr.Zero;
        }
        #endregion

        #region 字符串处理
        /// <summary>
        /// 转换Unicode字符串到Ansi字符串
        /// </summary>
        /// <param name="str">Unicode字符串</param>
        /// <returns>Ansi字符串（字节数组格式）</returns>
        private byte[] StringToAnsiZ(string str)
        {
            //' Convert a Unicode string to a null terminated Ansi string for Ghostscript.  
            //' The result is stored in a byte array. Later you will need to convert  
            //' this byte array to a pointer with GCHandle.Alloc(XXXX, GCHandleType.Pinned)  
            //' and GSHandle.AddrOfPinnedObject()  
            int intElementCount;
            int intCounter;
            byte[] aAnsi;
            byte bChar;
            intElementCount = str.Length;
            aAnsi = new byte[intElementCount + 1];
            for (intCounter = 0; intCounter < intElementCount; intCounter++)
            {
                bChar = (byte)str[intCounter];
                aAnsi[intCounter] = bChar;
            }
            aAnsi[intElementCount] = 0;
            return aAnsi;
        }
        #endregion

        #region 转换文件
        /// <summary>
        /// 转换文件
        /// </summary>
        /// <param name="inputFile">输入的PDF文件路径</param>
        /// <param name="outputFile">输出的Jpeg图片路径</param>
        /// <param name="firstPage">第一页</param>
        /// <param name="lastPage">最后一页</param>
        /// <param name="deviceFormat">格式（文件格式）</param>
        /// <param name="width">宽度</param>
        /// <param name="height">高度</param>
        public void Convert(string inputFile, string outputFile,
            int firstPage, int lastPage, string deviceFormat, int width, int height)
        {
            //判断文件是否存在
            if (!System.IO.File.Exists(inputFile))
            {
                LogHandler.LogWrite(string.Format("文件{0}不存在", inputFile));
                return;
            }
            int intReturn;
            IntPtr intGSInstanceHandle;
            object[] aAnsiArgs;
            IntPtr[] aPtrArgs;
            GCHandle[] aGCHandle;
            int intCounter;
            int intElementCount;
            IntPtr callerHandle;
            GCHandle gchandleArgs;
            IntPtr intptrArgs;
            string[] sArgs = GetGeneratedArgs(inputFile, outputFile,
                firstPage, lastPage, deviceFormat, width, height);
            // Convert the Unicode strings to null terminated ANSI byte arrays  
            // then get pointers to the byte arrays.  
            intElementCount = sArgs.Length;
            aAnsiArgs = new object[intElementCount];
            aPtrArgs = new IntPtr[intElementCount];
            aGCHandle = new GCHandle[intElementCount];
            // Create a handle for each of the arguments after   
            // they've been converted to an ANSI null terminated  
            // string. Then store the pointers for each of the handles  
            for (intCounter = 0; intCounter < intElementCount; intCounter++)
            {
                aAnsiArgs[intCounter] = StringToAnsiZ(sArgs[intCounter]);
                aGCHandle[intCounter] = GCHandle.Alloc(aAnsiArgs[intCounter], GCHandleType.Pinned);
                aPtrArgs[intCounter] = aGCHandle[intCounter].AddrOfPinnedObject();
            }
            // Get a new handle for the array of argument pointers  
            gchandleArgs = GCHandle.Alloc(aPtrArgs, GCHandleType.Pinned);
            intptrArgs = gchandleArgs.AddrOfPinnedObject();
            intReturn = gsapi_new_instance(out intGSInstanceHandle, _objHandle);
            callerHandle = IntPtr.Zero;
            try
            {
                intReturn = gsapi_init_with_args(intGSInstanceHandle, intElementCount, intptrArgs);
            }
            catch (Exception ex)
            {
                 LogHandler.LogWrite(string.Format("PDF文件{0}转换失败.
错误:{1}",new string[]{inputFile,ex.ToString()}));

            }
            finally
            {
                for (intCounter = 0; intCounter < intReturn; intCounter++)
                {
                    aGCHandle[intCounter].Free();
                }
                gchandleArgs.Free();
                gsapi_exit(intGSInstanceHandle);
                gsapi_delete_instance(intGSInstanceHandle);
            }
        }
        #endregion

        #region 转换文件
        /// <summary>
        /// 
        /// </summary>
        /// <param name="inputFile"></param>
        /// <param name="outputFile"></param>
        /// <param name="firstPage"></param>
        /// <param name="lastPage"></param>
        /// <param name="deviceFormat"></param>
        /// <param name="width"></param>
        /// <param name="height"></param>
        /// <returns></returns>
        private string[] GetGeneratedArgs(string inputFile, string outputFile,
            int firstPage, int lastPage, string deviceFormat, int width, int height)
        {
            this._sDeviceFormat = deviceFormat;
            this._iResolutionX = width;
            this._iResolutionY = height;
            // Count how many extra args are need - HRangel - 11/29/2006, 3:13:43 PM  
            ArrayList lstExtraArgs = new ArrayList();
            if (_sDeviceFormat == "jpg" && _iJPEGQuality > 0 && _iJPEGQuality < 101)
                lstExtraArgs.Add("-dJPEGQ=" + _iJPEGQuality);
            if (_iWidth > 0 && _iHeight > 0)
                lstExtraArgs.Add("-g" + _iWidth + "x" + _iHeight);
            if (_bFitPage)
                lstExtraArgs.Add("-dPDFFitPage");
            if (_iResolutionX > 0)
            {
                if (_iResolutionY > 0)
                    lstExtraArgs.Add("-r" + _iResolutionX + "x" + _iResolutionY);
                else
                    lstExtraArgs.Add("-r" + _iResolutionX);
            }
            // Load Fixed Args - HRangel - 11/29/2006, 3:34:02 PM  
            int iFixedCount = 17;
            int iExtraArgsCount = lstExtraArgs.Count;
            string[] args = new string[iFixedCount + lstExtraArgs.Count];
            /* 
            // Keep gs from writing information to standard output 
        "-q",                      
        "-dQUIET", 

        "-dPARANOIDSAFER", // Run this command in safe mode 
        "-dBATCH", // Keep gs from going into interactive mode 
        "-dNOPAUSE", // Do not prompt and pause for each page 
        "-dNOPROMPT", // Disable prompts for user interaction            
        "-dMaxBitmap=500000000", // Set high for better performance 

        // Set the starting and ending pages 
        String.Format("-dFirstPage={0}", firstPage), 
        String.Format("-dLastPage={0}", lastPage),    

        // Configure the output anti-aliasing, resolution, etc 
        "-dAlignToPixels=0", 
        "-dGridFitTT=0", 
        "-sDEVICE=jpeg", 
        "-dTextAlphaBits=4", 
        "-dGraphicsAlphaBits=4", 
            */
            args[0] = "pdf2img";//this parameter have little real use  
            args[1] = "-dNOPAUSE";//I don't want interruptions  
            args[2] = "-dBATCH";//stop after  
            //args[3]="-dSAFER";  
            args[3] = "-dPARANOIDSAFER";
            args[4] = "-sDEVICE=" + _sDeviceFormat;//what kind of export format i should provide  
            args[5] = "-q";
            args[6] = "-dQUIET";
            args[7] = "-dNOPROMPT";
            args[8] = "-dMaxBitmap=500000000";
            args[9] = String.Format("-dFirstPage={0}", firstPage);
            args[10] = String.Format("-dLastPage={0}", lastPage);
            args[11] = "-dAlignToPixels=0";
            args[12] = "-dGridFitTT=0";
            args[13] = "-dTextAlphaBits=4";
            args[14] = "-dGraphicsAlphaBits=4";
            //For a complete list watch here:  
            //http://pages.cs.wisc.edu/~ghost/doc/cvs/Devices.htm  
            //Fill the remaining parameters  
            for (int i = 0; i < iExtraArgsCount; i++)
            {
                args[15 + i] = (string)lstExtraArgs[i];
            }
            //Fill outputfile and inputfile  
            args[15 + iExtraArgsCount] = string.Format("-sOutputFile={0}", outputFile);
            args[16 + iExtraArgsCount] = string.Format("{0}", inputFile);
            return args;
        }
        #endregion


    }
}

 OCR，识别Image代码（AsPrise辅助类）

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;

namespace PDFCaptureService
{
    public static class AspriseOCRHandler
    {
        #region 外部引用
        [DllImport("AspriseOCR.dll", EntryPoint = "OCR", CallingConvention = CallingConvention.Cdecl)]
        public static extern IntPtr OCR(string file, int type);
        [DllImport("AspriseOCR.dll", EntryPoint = "OCRpart", CallingConvention = CallingConvention.Cdecl)]
        static extern IntPtr OCRpart(string file, int type, int startX, int
        startY, int width, int height);
        [DllImport("AspriseOCR.dll", EntryPoint = "OCRBarCodes", CallingConvention = CallingConvention.Cdecl)]
        static extern IntPtr OCRBarCodes(string file, int type);
        [DllImport("AspriseOCR.dll", EntryPoint = "OCRpartBarCodes", CallingConvention = CallingConvention.Cdecl)]
        static extern IntPtr OCRpartBarCodes(string file, int type, int
        startX, int startY, int width, int height);
        #endregion

        /// <summary>
        /// 
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string ReadImage(string fileName)
        {
            IntPtr ptrFileContent = OCR(fileName, -1);
            string fileContent = Marshal.PtrToStringAnsi(ptrFileContent);
            //
            return fileContent;
        }
    }
}

 调用示例

GhostscriptHandler ghostscriptHandler = new GhostscriptHandler();
                        string tempJpgFileName = string.Format(GhostScriptImageName, Guid.NewGuid().ToString());
                        int pdfPageCount = ITextSharpHandler.GetPdfPageCount(fileName);
                        ghostscriptHandler.Convert(fileName, tempJpgFileName, 1, pdfPageCount, "jpeg", 100, 100);
                        fileContent = AspriseOCRHandler.ReadImage(fileName);