请问vc中如何把数据库中的jpeg文件读出并显示出来?

Question

谢了先!!

Answer 1

HRESULT   hr;
HDC hdc;
char *pBuf;
VARIANT varBLOB;
VARIANT rgvValues;
BSTR Bstr1;
long lDataSize;
COleVariant rValueData;
hr=CoInitialize(NULL);
CString Constr,wCmdString;
CComPtr<ADOField> pField;
// if(FAILED(hr))
m_Conn = NULL;
m_Rec = NULL;
pFields = NULL;
hr = ::CoCreateInstance((REFCLSID)CLSID_CADOConnection,NULL,CLSCTX_INPROC_SERVER,\
(REFIID)IID_IADOConnection,(LPVOID*)&m_Conn);
if (FAILED(hr))
return ;
hr = ::CoCreateInstance((REFCLSID)CLSID_CADORecordset,NULL,CLSCTX_INPROC_SERVER,\
(REFIID)IID_IADORecordset,(LPVOID*)&m_Rec);
if (FAILED(hr))
return ;
Constr="Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+tempstr+";Persist Security Info=False";
hr = m_Conn->Open(CComBSTR(Constr),CComBSTR(""),CComBSTR(""),adOpenUnspecified);
if (FAILED(hr))
{
::AfxMessageBox("连接数据库错误！");
return ;
}
wCmdString=_T("select * from userphoto");//
hr = m_Rec->Open(CComVariant(wCmdString),CComVariant(m_Conn),adOpenKeyset,adLockOptimistic,adCmdText);
if (FAILED(hr))
{
::AfxMessageBox("打开表错误！");
return ;
}
m_Rec->get_Collect(CComVariant(1),rValueData);
Bstr1= (_bstr_t) rValueData;
m_UserName.Format("%s",(CString)Bstr1);
rValueData.Clear(); 
m_Rec->get_Collect(CComVariant(2),rValueData);    ///为新记录填充username字段
m_UseOld=rValueData.intVal;
pField=NULL;
m_Rec->get_Fields(&pFields);//加入BLOB类型的数据
pFields->get_Item(CComVariant(3),&pField);
pField->get_ActualSize(&lDataSize);
if(lDataSize > 0)
{
rgvValues.vt = VT_ERROR;
rgvValues.scode = DISP_E_PARAMNOTFOUND;
pField->GetChunk(lDataSize,&varBLOB);
if(varBLOB.vt == (VT_ARRAY | VT_UI1))                                 ///判断数据类型是否正确
{
SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);              ///得到指向数据的指针
/*****在这里我们可以对pBuf中的数据进行处理*****/
SafeArrayUnaccessData (varBLOB.parray);
}
}
hdc=::GetDC(m_Show.m_hWnd);
CRect r_Show;
m_Show.GetClientRect(r_Show);
int xpos=r_Show.left;
int ypos=r_Show.top;// IPicture *pPic; 
IStream *pStm; 
HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, lDataSize); 
LPVOID pvData = NULL; 
if (hGlobal != NULL) 
{ 
if ((pvData = GlobalLock(hGlobal)) != NULL) 
{ 
memcpy(pvData,pBuf,lDataSize);
GlobalUnlock(hGlobal); 
CreateStreamOnHGlobal(hGlobal, TRUE, &pStm); 
if(SUCCEEDED(OleLoadPicture(pStm,lDataSize,TRUE,IID_IPicture,(LPVOID*)&pPic))) 
{ 
m_ok=TRUE;
OLE_XSIZE_HIMETRIC hmWidth; 
OLE_YSIZE_HIMETRIC hmHeight; 
pPic->get_Width(&hmWidth); 
pPic->get_Height(&hmHeight); 
double fX,fY; 
fX = r_Show.Width();
fY = r_Show.Height();
if(FAILED(pPic->Render(hdc,xpos,ypos,(DWORD)fX,(DWORD)fY,0,hmHeight,hmWidth,-hmHeight,NULL))) 
AfxMessageBox("Failed To Render The picture!"); 
// pPic->Release(); 
} 
else 
AfxMessageBox("Error Loading Picture From Stream!"); 
} 
} 
GlobalFree(hGlobal);