用VB6读写数据库中的图片

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1，以人名和相关图片为例说明，数据库为Access，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
注释： Return a temporary file name.
Private Function TemporaryFileName() As String
Dim temp_path As String
Dim temp_file As String
Dim length As Long

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

注释： 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

注释： 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"

注释： 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"

注释： 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

注释： 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

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

注释： Get a temporary file name.
file_name = TemporaryFileName()

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

注释： 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

注释： 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

注释： 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
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