用过GDI+的高手请进来指点一下

[chenchongpan]

为什么下面的代码返回的指针一直为NULL，使用FromFile需要什么前提条件？

Image *image;
//加载位图、旋转、保存
USES_CONVERSION;
image=Image::FromFile(A2W((LPCTSTR)sFilePathName),FALSE);

注：stdafx.h中已经包含了如下头文件
#include <afxpriv2.h>
#define ULONG_PTR DWORD
#include "GDIPlus\gdiplus.h"
using namespace Gdiplus;

[masterz]

have you initialized GDI+?

GdiplusStartupInput gdiplusStartupInput;
ULONG gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
full program:
#include <Stdio.h>
#include <Objbase.h>
#include <Windows.h>
#include <Gdiplus.h>
#include <GdiPlusEnums.h>
using namespace Gdiplus;
#pragma comment(lib,"gdiplus")
int GetCodecClsid(const WCHAR*, CLSID*);
HRESULT __fastcall AnsiToUnicode(LPCSTR pszA, LPOLESTR* ppszW)
{
ULONG cCharacters;
DWORD dwError;
if (NULL == pszA)
{
*ppszW = NULL;
return NOERROR;
}
cCharacters = strlen(pszA)+1;
*ppszW = (LPOLESTR) CoTaskMemAlloc(cCharacters*2);
if (NULL == *ppszW)
return E_OUTOFMEMORY;
if (0 == MultiByteToWideChar(CP_ACP, 0, pszA, cCharacters,*ppszW, cCharacters))
{
dwError = GetLastError();
CoTaskMemFree(*ppszW);
*ppszW = NULL;
return HRESULT_FROM_WIN32(dwError);
}
return NOERROR;
}

int main(int argc, char* argv[])
{
int n_ret=0;
printf("%s can convert jpg, png, gif, tiff to gif file.\n if it works, it is written by masterz, otherwise I don't know who write it\n",argv[0]);
if(argc!=3)
{
printf("usage:%s gif_filename source_image_filename\n",argv[0]);
return -1;
}
GdiplusStartupInput gdiplusStartupInput;
ULONG gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
{
CLSID codecClsid;
Status stat;
EncoderParameters encoderParameters;

GetCodecClsid(L"image/gif", &codecClsid);
encoderParameters.Count = 0;
LPOLESTR bstr_src_img;
LPOLESTR bstr_dst_fn;
AnsiToUnicode(argv[1],&bstr_dst_fn);
AnsiToUnicode(argv[2],&bstr_src_img);
Image image(bstr_src_img);
stat =image.Save(bstr_dst_fn, &codecClsid, &encoderParameters);
if(stat == Ok)
{
n_ret=0;
wprintf(L"%s saved successfully.\n",bstr_dst_fn);
}
else
{
n_ret=-2;
wprintf(L"%d Attempt to save %s failed.\n", stat, bstr_dst_fn);
}
CoTaskMemFree(bstr_dst_fn);
CoTaskMemFree(bstr_src_img);
}
GdiplusShutdown(gdiplusToken);
return 0;
} // main
int GetCodecClsid(const WCHAR* format, CLSID* pClsid)
{
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytes

ImageCodecInfo* pImageCodecInfo = NULL;

GetImageEncodersSize(&num, &size);
if(size == 0)
return -1; // Failure

pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
if(pImageCodecInfo == NULL)
return -1; // Failure

GetImageEncoders(num, size, pImageCodecInfo);

for(UINT j = 0; j < num; ++j)
{
if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
{
*pClsid = pImageCodecInfo[j].Clsid;
return j; // Success
}
} // for

return -1; // Failure

} // GetCodecClsid
//in order to compile this program, you need to download microsoft platform sdk from http://www.microsoft.com/msdownload/platformsdk/sdkupdate/downlevel.htm
//also download gdiplus.dll and put it at the same directory as the executable.
//http://www.microsoft.com/downloads/release.asp?releaseid=32738
//Platform SDK Redistributable: GDI+ RTM

//sample usage: img2gif a.gif src.bmp

[chenchongpan]

多谢指点！