大致这样，pData为缓冲区
HGLOBAL hBuffer=GlobalAlloc(GMEM_MOVEABLE,imageSize);
void* pBuffer=GlobalLock(hBuffer);
CopyMemory(pBuffer, pData, imageSize);
IStream* pStream=NULL;
CreateStreamOnHGlobal(hBuffer,FALSE,&pStream);
Bitmap bm(pStream);
CLSID pngClsid;
GetEncoderClsid(L"image/jpeg", &pngClsid);
//bm.Save(L"xx.jpg", &pngClsid, NULL);
HGLOBAL hBuffer2=GlobalAlloc(GMEM_MOVEABLE,imageSize2);
IStream* pStream2=NULL;
CreateStreamOnHGlobal(hBuffer,FALSE,&pStream2);
bm.Save(pStream2, &pngClsid, NULL);
void* pBuffer2=GlobalLock(hBuffer2);
CopyMemory(pData, pBuffer2, imageSize2);
GlobalUnlock(hBuffer);
GlobalFree(hBuffer);
GlobalUnlock(hBuffer2);
GlobalFree(hBuffer2);
