📄 关于用vc，vb进行图像数据（二进制大对象）存储数据库的一点心得 .htm
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关于用VC，VB进行图像数据（二进制大对象）存储数据库的一点心得
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关于用VC，VB进行图像数据（二进制大对象）存储数据库的一点心得
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<B>关键字:</B><BR>
ADO,BLOB，图像数据
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<B>贴文时间</B><br>
2001-5-5 16:05:09
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<B>文章类型: </B><BR>
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<br><br><P> 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。</P>
<P> 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，也请这方面的高手多多指教。（均用ADO连接数据库）</P>
<P><FONT face=System>1. VC把一个文件存入数据库</FONT></P>
<P><FONT face=System> CFile imagefile;<BR> if(0 == imagefile.Open("d:\\user\\bmp.bmp",CFile::modeRead))<BR> return;<BR> _RecordsetPtr pRs = NULL; <BR> _ConnectionPtr pConnection = NULL;<BR> _variant_t varChunk;<BR> HRESULT hr;<BR> BYTE* pbuf;<BR> long nLength = imagefile.GetLength();<BR> pbuf = new BYTE[nLength+2];<BR> if(pbuf == NULL)<BR> return; //allocate memory error;<BR> imagefile.Read(pbuf,nLength); //read the file into memory</FONT></P>
<P><FONT face=System> BYTE *pBufEx;<BR> pBufEx = pbuf;<BR> //build a SAFFERRAY<BR> SAFEARRAY* psa;<BR> SAFEARRAYBOUND rgsabound[1];<BR> rgsabound[0].lLbound = 0;<BR> rgsabound[0].cElements = nLength;<BR> psa = SafeArrayCreate(VT_UI1, 1, rgsabound);</FONT></P>
<P><FONT face=System> for (long i = 0; i < nLength; i++)<BR> SafeArrayPutElement (psa, &i, pBufEx++);<BR> VARIANT varBLOB;<BR> varBLOB.vt = VT_ARRAY | VT_UI1;<BR> varBLOB.parray = psa;</FONT></P>
<P><FONT face=System> _bstr_t strCnn("Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"); <BR> try<BR> {<BR> //Open a connection<BR> pConnection.CreateInstance(__uuidof(Connection));<BR> hr = pConnection->Open(strCnn,"","",NULL); //Connect a DataBase<BR> pRs.CreateInstance(__uuidof(Recordset));<BR> pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable); //Open a Table<BR> <BR>// pRs->AddNew(); <BR> pRs->Fields->GetItem("Image")->AppendChunk(varBLOB); <BR> pRs->Update();<BR> pRs->Close();<BR> pConnection->Close();<BR> }<BR> catch(_com_error &e)<BR> {<BR> // Notify the user of errors if any.<BR> _bstr_t bstrSource(e.Source());<BR> _bstr_t bstrDescription(e.Description());<BR> CString sError;<BR> sError.Format("Source : %s \n Description : %s\n",(LPCSTR)bstrSource,(LPCSTR)bstrDescription);<BR> AfxMessageBox(sError); <BR> }</FONT></P>
<P><FONT face=System>2. VC把数据库中IMAGE字段取出存为文件</FONT></P>
<P><FONT face=System> _RecordsetPtr pRs = NULL;<BR> _ConnectionPtr pConnection = NULL;<BR> _variant_t varChunk;<BR> HRESULT hr;<BR> VARIANT varBLOB;<BR> _bstr_t strCnn("Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"); <BR> try<BR> {<BR> //Open a connection<BR> pConnection.CreateInstance(__uuidof(Connection));<BR> hr = pConnection->Open(strCnn,"","",NULL); <BR> pRs.CreateInstance(__uuidof(Recordset));<BR> pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable);<BR> //read data <BR> long lDataLength = pRs->Fields->GetItem("Image")->ActualSize;<BR> varBLOB = pRs->GetFields()->GetItem("Image")->GetChunk(lDataLength);<BR> if(varBLOB.vt == (VT_ARRAY | VT_UI1)) <BR> {<BR> BYTE *pBuf = NULL; <BR> pBuf = (BYTE*)GlobalAlloc(GMEM_FIXED,lDataLength);<BR> SafeArrayAccessData(varBLOB.parray,(void **)pBuf); <BR> //Build a File in Windows Temp Directory<BR> char tmpPath[_MAX_PATH+1];<BR> GetTempPath(_MAX_PATH,tmpPath);<BR> CString strFileName = "temp.bmp";<BR> strFileName = tmpPath+strFileName;<BR> <BR> CFile outFile(strFileName,CFile::modeCreate|CFile::modeWrite);<BR> LPSTR buffer = (LPSTR)GlobalLock((HGLOBAL)pBuf);<BR> outFile.WriteHuge(buffer,lDataLength);<BR> GlobalUnlock((HGLOBAL)pBuf);<BR> outFile.Close(); <BR> SafeArrayUnaccessData (varBLOB.parray);<BR> }</FONT></P>
<P><FONT face=System> pRs->Close();<BR> pConnection->Close();<BR> }<BR> catch(_com_error &e)<BR> {<BR> // Notify the user of errors if any.<BR> _bstr_t bstrSource(e.Source());<BR> _bstr_t bstrDescription(e.Description());<BR> CString sError;<BR> sError.Format("Source : %s \n Description : %s\n",(LPCSTR)bstrSource,(LPCSTR)bstrDescription);<BR> AfxMessageBox(sError); <BR> } </FONT></P>
<P><FONT face=System>3. VB把文件存入数据库IMAGE字段</FONT></P>
<P><FONT face=System>Sub savepic(FileName As String, IndexNumber As Long)<BR> Dim DcnNWind As New ADODB.Connection<BR> Dim rs As ADODB.Recordset<BR> Set rs = New ADODB.Recordset<BR> DcnNWind.CursorLocation = adUseClient<BR> DcnNWind.Open "Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"<BR> rs.CursorType = adOpenKeyset<BR> rs.LockType = adLockOptimistic<BR> rs.Open "CustomInfo", DcnNWind, , adCmdTable<BR> rs.Move (IndexNumber)<BR> Call FileToBlob(rs.Fields("Image"), FileName, FileLen(FileName))<BR> rs.UpdateBatch adAffectCurrent<BR>End Sub</FONT></P>
<P><FONT face=System>Private Sub FileToBlob(fld As ADODB.Field, FileName As String, Optional ChunkSize As Long )<BR> Dim fnum As Integer, bytesLeft As Long, bytes As Long<BR> Dim tmp() As Byte<BR> If (fld.Attributes And adFldLong) = 0 Then<BR> Err.Raise 1001, , "Field doesn't support the GetChunk method."<BR> End If<BR> fnum = FreeFile<BR> Open FileName For Binary As fnum<BR> bytesLeft = LOF(fnum)<BR> Do While bytesLeft<BR> bytes = bytesLeft<BR> If bytes > ChunkSize Then bytes = ChunkSize<BR> ReDim tmp(1 To bytes) As Byte<BR> Get #1, , tmp<BR> fld.AppendChunk tmp<BR> bytesLeft = bytesLeft - bytes<BR> Loop<BR> Close #fnum<BR>End Sub</FONT></P>
<P><FONT face=System>4. VB把文件从IMAGE字段中读到文件中。</FONT></P>
<P><FONT face=System>Sub loadpic(IndexNumber As Long)<BR> Dim DcnNWind As New ADODB.Connection<BR> Dim rs As ADODB.Recordset<BR> Set rs = New ADODB.Recordset<BR> DcnNWind.CursorLocation = adUseClient<BR> DcnNWind.Open "Provider=SQLOLEDB.1;Integrated Security=SSI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER"<BR> rs.CursorType = adOpenKeyset<BR> rs.LockType = adLockOptimistic<BR> rs.Open "CustomInfo", DcnNWind, , adCmdTable<BR> rs.Move (IndexNumber)<BR> Call BlobToFile(rs.Fields("Image"), "c:\windows\temp\tmp.bmp", rs.Fields("Image").ActualSize)<BR>End Sub</FONT></P>
<P><FONT face=System>Private Sub BlobToFile(fld As ADODB.Field, FileName As String, Optional ChunkSize As Long )<BR> Dim fnum As Integer, bytesLeft As Long, bytes As Long<BR> Dim tmp() As Byte<BR> If (fld.Attributes And adFldLong) = 0 Then<BR> Err.Raise 1001, , "Field doesn't support the GetChunk method."<BR> End If<BR> If Dir$(FileName) <> "" Then Kill FileName<BR> fnum = FreeFile<BR> Open FileName For Binary As fnum<BR> bytesLeft = fld.ActualSize<BR> Do While bytesLeft<BR> bytes = bytesLeft<BR> If bytes > ChunkSize Then bytes = ChunkSize<BR> tmp = fld.GetChunk(bytes)<BR> Put #fnum, , tmp<BR> bytesLeft = bytesLeft - bytes<BR> Loop<BR> Close #fnum<BR>End Sub</FONT></P><br><br>
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