using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Runtime.InteropServices; 
using System.Collections; 
/**
Convert PDF to Image Format(JPEG) using Ghostscript API

convert a pdf to jpeg using ghostscript command line:
gswin32c -q -dQUIET -dPARANOIDSAFER  -dBATCH -dNOPAUSE  -dNOPROMPT -dMaxBitmap=500000000 -dFirstPage=1 -dAlignToPixels=0 -dGridFitTT=0 -sDEVICE=jpeg -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -r100x100 -sOutputFile=output.jpg test.pdf
see also:http://www.mattephraim.com/blog/2009/01/06/a-simple-c-wrapper-for-ghostscript/
and: http://www.codeproject.com/KB/cs/GhostScriptUseWithCSharp.aspx
Note:copy gsdll32.dll to system32 directory before using this ghostscript wrapper.
 * 
 */ 
namespace ConvertPDF 
{ 
    /// summary> 
    ///  
    /// Class to convert a pdf to an image using GhostScript DLL 
    /// Credit for this code go to:Rangel Avulso 
    /// i only fix a little bug and refactor a little 
    /// http://www.hrangel.com.br/index.php/2006/12/04/converter-pdf-para-imagem-jpeg-em-c/ 
    /// /summary> 
    /// seealso cref="http://www.hrangel.com.br/index.php/2006/12/04/converter-pdf-para-imagem-jpeg-em-c/"/> 
    class PDFConvert 
    { 
        #region GhostScript Import 
        /// summary>Create a new instance of Ghostscript. 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().  
        /// /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.  
        /// /summary> 
        /// param name="instance">/param> 
        [DllImport("gsdll32.dll", EntryPoint="gsapi_delete_instance")] 
        private static extern void gsapi_delete_instance (IntPtr instance); 
        #endregion 
        #region Variables 
        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 Proprieties 
        public string OutputFormat 
        { 
            get { return _sDeviceFormat; } 
            set { _sDeviceFormat = value; } 
        } 
        public int Width 
        { 
            get { return _iWidth; } 
            set { _iWidth = value; } 
        } 
        public int Height 
        { 
            get { return _iHeight; } 
            set { _iHeight = value; } 
        } 
        public int ResolutionX 
        { 
            get { return _iResolutionX; } 
            set { _iResolutionX = value; } 
        } 
        public int ResolutionY 
        { 
            get { return _iResolutionY; } 
            set { _iResolutionY = value; } 
        } 
        public Boolean FitPage 
        { 
            get { return _bFitPage; } 
            set { _bFitPage = value; } 
        } 
        /// summary>Quality of compression of JPG/summary> 
        public int JPEGQuality 
        { 
            get { return _iJPEGQuality; } 
            set { _iJPEGQuality = value; } 
        } 
        #endregion 
        #region Init 
        public PDFConvert(IntPtr objHandle) 
        { 
            _objHandle = objHandle; 
        } 
        public PDFConvert() 
        { 
            _objHandle = IntPtr.Zero; 
        } 
        #endregion 
        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; 
        } 
        /// summary>Convert the file!/summary> 
        public void Convert(string inputFile,string outputFile, 
            int firstPage, int lastPage, string deviceFormat, int width, int height) 
        { 
            //Avoid to work when the file doesn't exist 
            if (!System.IO.File.Exists(inputFile)) 
            { 
                System.Windows.Forms.MessageBox.Show(string.Format("The file :'{0}' doesn't exist",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) 
            { 
                //System.Windows.Forms.MessageBox.Show(ex.Message); 

            } 
            finally 
            { 
                for (intCounter = 0; intCounter intReturn; intCounter++) 
                { 
                    aGCHandle[intCounter].Free(); 
                } 
                gchandleArgs.Free(); 
                gsapi_exit(intGSInstanceHandle); 
                gsapi_delete_instance(intGSInstanceHandle); 
            } 
        } 
        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; 
        } 
        public void pdf2jpgTest() 
        {             
            this.Convert(@"C://tmp//pdfimg//test1.pdf",@"C://tmp//pdfimg//out.jpg",1,1,"jpeg",100,100); 
            //this.Convert(@"C://tmp//pdfimg//test.pdf", @"C://tmp//pdfimg//out2.jpg", 291, 291, "jpeg", 800, 800); 
        } 
    } 
} 

 PDFConvert convertor = new PDFConvert();
 convertor.pdf2jpgTest();
 

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 
using ConvertPDF; 
namespace PDF2Img 
{ 
    public partial class Form1 : Form 
    { 
        public Form1() 
        { 
            InitializeComponent(); 

        } 
        private void button1_Click(object sender, EventArgs e) 
        { 
            PDFConvert convertor = new PDFConvert(); 
            convertor.pdf2jpgTest(); 
            Image img = Image.FromFile(@"C://tmp//pdfimg//out.jpg"); 
            myBitmap = new Bitmap(img); 

            Graphics G = this.CreateGraphics(); 
            GraphicsUnit GU = G.PageUnit; 
            BMPContainer = myBitmap.GetBounds(ref GU); //X,Y = 0 

           // Graphics g = this.CreateGraphics(); 
            //g.DrawImage(myBitmap, 1, 1); 
            this.Invalidate(); 
        } 
        private Bitmap myBitmap; 
        private RectangleF BMPContainer; 
        protected override void OnPaint(PaintEventArgs e) 
        { 
            Graphics G = e.Graphics; 
            if (myBitmap != null) 
            {            
                G.DrawImage(myBitmap, BMPContainer); 
            } 
            base.OnPaint(e); 
        } 
    } 
}