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pdf转换成jpg示例分享_实用技巧_
2023-05-24
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简介 pdf转换成jpg示例分享_实用技巧_
复制代码 代码如下:
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
{
///
///
/// 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/
///
///
class PDFConvert
{
#region GhostScript Import
///
/// At this stage, Ghostscript supports only one instance.
///
///
///
[DllImport("gsdll32.dll", EntryPoint="gsapi_new_instance")]
private static extern int gsapi_new_instance (out IntPtr pinstance, IntPtr caller_handle);
///
///
///
///
///
[DllImport("gsdll32.dll", EntryPoint="gsapi_init_with_args")]
private static extern int gsapi_init_with_args (IntPtr instance, int argc, IntPtr argv);
///
/// Exit the interpreter. This must be called on shutdown if gsapi_init_with_args() has been called, and just before gsapi_delete_instance().
///
///
///
[DllImport("gsdll32.dll", EntryPoint="gsapi_exit")]
private static extern int gsapi_exit (IntPtr instance);
///
/// 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.
///
///
[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; }
}
///
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;
}
///
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=" + _iJPEGQu
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