VC/VB 进行图像数据存储数据库心得

2005-06-22 10:14 出处: 作者:mynote 责任编辑:moningfeng
网上经常有人问如何把图像存入数据库中,原先我也是不得要领。经过多方指点和自己在开发过程中的摸索,终于解决这一问题。下面给出用VC,VB如何操作图像文件存取数据库的原码,帮助一些还没有掌握方法的朋友(均用ADO连接数据库)。

一、VC把一个文件存入数据库

CFile imagefile; if(0 == imagefile.Open("d:\\user\\bmp.bmp",CFile::modeRead)) return; _RecordsetPtr pRs = NULL; _ConnectionPtr pConnection = NULL; _variant_t varChunk; HRESULT hr; BYTE* pbuf; long nLength = imagefile.GetLength(); pbuf = new BYTE[nLength+2]; if(pbuf == NULL) return; //allocate memory error; imagefile.Read(pbuf,nLength); //read the file into memory BYTE *pBufEx; pBufEx = pbuf; //build a SAFFERRAY SAFEARRAY* psa; SAFEARRAYBOUND rgsabound[1]; rgsabound[0].lLbound = 0; rgsabound[0].cElements = nLength; psa = SafeArrayCreate(VT_UI1, 1, rgsabound); for (long i = 0; i < nLength; i++) SafeArrayPutElement (psa, &i, pBufEx++); VARIANT varBLOB; varBLOB.vt = VT_ARRAY | VT_UI1; varBLOB.parray = psa; _bstr_t strCnn("Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"); try { //Open a connection pConnection.CreateInstance(__uuidof(Connection)); hr = pConnection->Open(strCnn,"","",NULL); //Connect a DataBase pRs.CreateInstance(__uuidof(Recordset)); pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable); //Open a Table // pRs->AddNew(); pRs->Fields->GetItem("Image")->AppendChunk(varBLOB); pRs->Update(); pRs->Close(); pConnection->Close(); } catch(_com_error &e) { // Notify the user of errors if any. _bstr_t bstrSource(e.Source()); _bstr_t bstrDescription(e.Description()); CString sError; sError.Format("Source : %s \n Description : %s\n",(LPCSTR)bstrSource,(LPCSTR)bstrDescription); AfxMessageBox(sError); }

   二、VC把数据库中IMAGE字段取出存为文件

_RecordsetPtr pRs = NULL; _ConnectionPtr pConnection = NULL; _variant_t varChunk; HRESULT hr; VARIANT varBLOB; _bstr_t strCnn("Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"); try { //Open a connection pConnection.CreateInstance(__uuidof(Connection)); hr = pConnection->Open(strCnn,"","",NULL); pRs.CreateInstance(__uuidof(Recordset)); pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable); //read data long lDataLength = pRs->Fields->GetItem("Image")->ActualSize; varBLOB = pRs->GetFields()->GetItem("Image")->GetChunk(lDataLength); if(varBLOB.vt == (VT_ARRAY | VT_UI1)) { BYTE *pBuf = NULL; pBuf = (BYTE*)GlobalAlloc(GMEM_FIXED,lDataLength); SafeArrayAccessData(varBLOB.parray,(void **)pBuf); //Build a File in Windows Temp Directory char tmpPath[_MAX_PATH+1]; GetTempPath(_MAX_PATH,tmpPath); CString strFileName = "temp.bmp"; strFileName = tmpPath+strFileName; CFile outFile(strFileName,CFile::modeCreate|CFile::modeWrite); LPSTR buffer = (LPSTR)GlobalLock((HGLOBAL)pBuf); outFile.WriteHuge(buffer,lDataLength); GlobalUnlock((HGLOBAL)pBuf); outFile.Close(); SafeArrayUnaccessData (varBLOB.parray); }

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