如何用VB6读写数据库中的图片

　 很多人问关于VB6读写数据库中的图片的问题，在此有一例，希有所启发。  
1，以人名和相关图片为例说明，数据库为Aclearcase/" target="_blank" >ccess，有如下字段：Name  
char,picture OLE object,FileLength Number。当为ms sql时，将picture改为lob即
可。  
2，示例包含control：commom dialog,picture,listbox。  
源码如下：  
Option Explicit  

Private Declare Function GetTempFileName Lib "kernel32" Alias "GetTempFileNameA"  
(ByVal lpszPath As String, ByVal lpPrefixString As String, ByVal wUnique As Long,  
ByVal lpTempFileName As String) As Long  
Private Declare Function GetTempPath Lib "kernel32" Alias "GetTempPathA" (ByVal  
nBufferLength As Long, ByVal lpBuffer As String) As Long  
Private Const MAX_PATH = 260  

Private m_DBConn As ADODB.Connection  

Private Const BLOCK_SIZE = 10000  
' Return a temporary file name.  
Private Function TemporaryFileName() As String  
Dim temp_path As String  
Dim temp_file As String  
Dim length As Long  

' Get the temporary file path.  
temp_path = Space$(MAX_PATH)  
length = GetTempPath(MAX_PATH, temp_path)  
temp_path = Left$(temp_path, length)  

' Get the file name.  
temp_file = Space$(MAX_PATH)  
GetTempFileName temp_path, "per", 0, temp_file  
TemporaryFileName = Left$(temp_file, InStr(temp_file, Chr$(0)) - 1)  
End Function  
Private Sub Form_Load()  
Dim db_file As String  
Dim rs As ADODB.Recordset  

' Get the database file name.  
db_file = App.Path  
If Right$(db_file, 1) <> "\" Then db_file = db_file & "\"  
db_file = db_file & "dbpict.mdb"  

' Open the database connection.  
Set m_DBConn = New ADODB.Connection  
m_DBConn.Open _  
"Provider=Microsoft.Jet.OLEDB.4.0;" & _  
"Data Source=" & db_file & ";" & _  
"Persist Security Info=False"  

' Get the list of people.  
Set rs = m_DBConn.Execute("SELECT Name FROM People ORDER BY Name", ,  
adCmdText)  
Do While Not rs.EOF  
lstPeople.AddItem rs!Name  
rs.MoveNext  
Loop  

rs.Close  
Set rs = Nothing  
End Sub  
Private Sub Form_Resize()  
lstPeople.Height = ScaleHeight  
End Sub  


' Display the clicked person.  
Private Sub lstPeople_Click()  
Dim rs As ADODB.Recordset  
Dim bytes() As Byte  
Dim file_name As String  
Dim file_num As Integer  
Dim file_length As Long  
Dim num_blocks As Long  
Dim left_over As Long  
Dim block_num As Long  
Dim hgt As Single  

picPerson.Visible = False  
Screen.MousePointer = vbHourglass  
DoEvents  

' Get the record.  
Set rs = m_DBConn.Execute("SELECT * FROM People WHERE Name='" & _  
lstPeople.Text & "'", , adCmdText)  
If rs.EOF Then Exit Sub  

' Get a temporary file name.  
file_name = TemporaryFileName()  

' Open the file.  
file_num = FreeFile  
Open file_name For Binary As #file_num  

' Copy the data into the file.  
file_length = rs!FileLength  
num_blocks = file_length / BLOCK_SIZE  
left_over = file_length Mod BLOCK_SIZE  

For block_num = 1 To num_blocks  
bytes() = rs!Picture.GetChunk(BLOCK_SIZE)  
Put #file_num, , bytes()  
Next block_num  

If left_over > 0 Then  
bytes() = rs!Picture.GetChunk(left_over)  
Put #file_num, , bytes()  
End If  

Close #file_num  

' Display the picture file.  
picPerson.Picture = LoadPicture(file_name)  
picPerson.Visible = True  

Width = picPerson.Left + picPerson.Width + Width - ScaleWidth  
hgt = picPerson.Top + picPerson.Height + Height - ScaleHeight  
If hgt < 1440 Then hgt = 1440  
Height = hgt  

Kill file_name  
Screen.MousePointer = vbDefault  
End Sub  

Private Sub mnuRecordAdd_Click()  
Dim rs As ADODB.Recordset  
Dim person_name As String  
Dim file_num As String  
Dim file_length As String  
Dim bytes() As Byte  
Dim num_blocks As Long  
Dim left_over As Long  
Dim block_num As Long  

person_name = InputBox("Name")  
If Len(person_name) = 0 Then Exit Sub  

dlgPicture.Flags = _  
cdlOFNFileMustExist Or _  
cdlOFNHideReadOnly Or _  
cdlOFNExplorer  
dlgPicture.CancelError = True  
dlgPicture.Filter = "Graphics Files|*.bmp;*.ico;*.jpg;*.gif"  

On Error Resume Next  
dlgPicture.ShowOpen  
If Err.Number = cdlCancel Then  
Exit Sub  
ElseIf Err.Number <> 0 Then  
MsgBox "Error " & Format$(Err.Number) & _  
" selecting file." & vbCrLf & Err.Description  
Exit Sub  
End If  

' Open the picture file.  
file_num = FreeFile  
Open dlgPicture.FileName For Binary Access Read As #file_num  

file_length = LOF(file_num)  
If file_length > 0 Then  
num_blocks = file_length / BLOCK_SIZE  
left_over = file_length Mod BLOCK_SIZE  

Set rs = New ADODB.Recordset  
rs.CursorType = adOpenKeyset  
rs.LockType = adLockOptimistic  
rs.Open "Select Name, Picture, FileLength FROM People", m_DBConn  

rs.AddNew  
rs!Name = person_name  
rs!FileLength = file_length  

ReDim bytes(BLOCK_SIZE)  
For block_num = 1 To num_blocks  
Get #file_num, , bytes()  
rs!Picture.AppendChunk bytes()  
Next block_num  

If left_over > 0 Then  
ReDim bytes(left_over)  
Get #file_num, , bytes()  
rs!Picture.AppendChunk bytes()  
End If  

rs.Update  
Close #file_num  

lstPeople.AddItem person_name  
lstPeople.Text = person_name  
End If  
End Sub

原文转自：http://www.ltesting.net