Knowledge Base

VB3 How to View Photos from the NWIND.MDB Database in VB

Article ID: 113957

Article Last Modified on 1/8/2003

APPLIES TO

Microsoft Visual Basic 3.0 Professional Edition

This article was previously published under Q113957

SUMMARY

This article shows by example how to view the photos in the Microsoft Access versions 1.x and 2.0 NWIND.MDB database.

NOTE: To run the code in this article, you will need to have both Microsoft Access version 1.x or 2.0 and the Microsoft Jet 2.0/Visual Basic 3.0 Compatibility Layer .DLL files.

MORE INFORMATION

Step-by-Step Example to View the Photos

Start a new project in Visual Basic. Form1 is created by default.
Add two Labels, two Text box controls, two Picture box controls and two Data controls to Form1.

Using the following table as a guide, set the properties of the controls you added in step 2.

   Control     Property               New Value
   ----------------------------------------------------------------
   Label1      Caption                Access 1.x
   Label2      Caption                Access 2.0
   Data1       DatabaseName           C:\ACCESS\NWIND.MDB
   Data1       RecordSource           Employees
   Data2       DatabaseName           C:\ACCESS2\SAMPAPPS\NWIND.MDB
   Data2       RecordSource           Employees

Place the following code in the (general) (declarations) section of MODULE1.BAS:

   Option Explicit

   Global Const LENGTH_FOR_SIZE = 4
   Global Const OBJECT_SIGNATURE = &H1C15
   Global Const OBJECT_HEADER_SIZE = 20
   Global Const CHECKSUM_SIGNATURE = &HFE05AD00
   Global Const CHECKSUM_STRING_SIZE = 4

   ' PT : Window sizing information for object
   '      Used in OBJECTHEADER type
   Type PT
      Width As Integer
      Height As Integer
   End Type

   ' OBJECTHEADER : Contains relevant information about object
   '
   Type OBJECTHEADER
      Signature As Integer         'Type signature (0x1c15)
      HeaderSize As Integer        'Size of header (sizeof(struct
                                   'OBJECTHEADER) + cchName +
                                   'cchClass)
      ObjectType As Long           'OLE Object type code (OT_STATIC,
                                   'OT_LINKED, OT_EMBEDDED)
      NameLen As Integer           'Count of characters in object
                                   'name (CchSz(szName) + 1)
      ClassLen As Integer          'Count of characters in class
                                   'name (CchSz(szClass) + 1)
      NameOffset As Integer        'Offset of object name in
                                   'structure (sizeof(OBJECTHEADER))
      ClassOffset As Integer       'Offset of class name in
                                   'structure (ibName + cchName)
      ObjectSize As PT             'Original size of object (see
                                   'code below for value)
      OleInfo As String * 256
   End Type

   Type OLEHEADER
      OleVersion As Long
      Format As Long
      OleInfo As String * 512
   End Type

   ' Enter each of the following Declare statements as one, single line:
   Declare Function GetTempFileName Lib "Kernel" (ByVal cDriveLetter As
      Integer, ByVal  lpPrefixString As String, ByVal wUnique As Integer,
      ByVal lpTempFileName As String) As Integer
   Declare Sub hmemcpy Lib "Kernel" (dest As Any, source As Any,
      ByVal bytes As Long)

   Function CopyOleBitmapToFile (OleField As Field) As String

      Const BUFFER_SIZE = 8192

      Dim tempFileName As String
      Dim Handle As Integer
      Dim Buffer As String

      Dim BytesNeeded As Long

      Dim Buffers As Long
      Dim Remainder As Long

      Dim ObjHeader As OBJECTHEADER
      Dim sOleHeader As String

      Dim ObjectOffset As Long
      Dim BitmapOffset As Long
      Dim BitmapHeaderOffset As Integer

      Dim r As Integer
      Dim i As Long

      tempFileName = ""
      If OleField.FieldSize() > OBJECT_HEADER_SIZE Then

         ' Get the Microsoft Access OLE header:
         sOleHeader = OleField.GetChunk(0, OBJECT_HEADER_SIZE)
         hmemcpy ObjHeader, ByVal sOleHeader, OBJECT_HEADER_SIZE

         ' Calculate the offset where the OLE object starts:
         ObjectOffset = ObjHeader.HeaderSize + 1

         ' Get enough bytes after the OLE header to get the bitmap header:
         Buffer = OleField.GetChunk(ObjectOffset, 512)

         ' Make sure the class of the object is a Paint Brush object:
         If Mid(Buffer, 12, 6) = "PBrush" Then

            BitmapHeaderOffset = InStr(Buffer, "BM")

            If BitmapHeaderOffset > 0 Then

               ' Calculate the beginning of the bitmap:
               BitmapOffset = ObjectOffset + BitmapHeaderOffset - 1

               ' Calculate the size of the bitmap:
               ' Enter the following two lines as one, single line:
               BytesNeeded = OleField.FieldSize() - OBJECT_HEADER_SIZE -
                  BitmapHeaderOffset - CHECKSUM_STRING_SIZE + 1

               ' Calculate the number of buffers needed to copy
               ' the OLE object based on the bitmap size:
               Buffers = BytesNeeded \ BUFFER_SIZE
               Remainder = BytesNeeded Mod BUFFER_SIZE

               ' Get a unique, temp filename:
               tempFileName = Space(255)
               r = GetTempFileName(0, "", -1, tempFileName)

               ' Copy the bitmap to the temporary file chunk by chunk:
               Handle = FreeFile
               Open tempFileName For Binary As #Handle

               For i = 0 To Buffers - 1
                  ' Enter the following two lines as one, single lin:
                  Buffer = OleField.GetChunk(BitmapOffset + i *
                     BUFFER_SIZE, BUFFER_SIZE)
                  Put #Handle, , Buffer
               Next

               ' Copy the remaining chunk of the bitmap to the file:
               ' Enter the following two lines as one, single line:
               Buffer = OleField.GetChunk(BitmapOffset + Buffers *
                  BUFFER_SIZE, Remainder)
               Put #Handle, , Buffer
               Close #Handle
            End If
         End If
      End If
      CopyOleBitmapToFile = Trim(tempFileName)
   End Function

   Sub DisplayOleBitmap (ctlPict As Control, OleField As Field)

      Const DT_LONGBINARY = 11

      Dim r As Integer
      Dim Handle As Integer
      Dim OleFileName As String

      If OleField.Type = DT_LONGBINARY Then

         OleFileName = CopyOleBitmapToFile(OleField)

         If OleFileName <> "" Then

            ' Display the bitmap:
            ctlPict.Picture = LoadPicture(OleFileName)

            ' Delete the temporary file:
            Kill OleFileName
         End If
      End If
   End Sub

Add the following to the Data1 Reposition event:

   Sub Data1_Reposition ()
      Screen.MousePointer = 11
      ' Make sure this is the current record:
      If Not (Data1.Recordset.EOF And Data1.Recordset.BOF) Then
         ' Change Photo to the name of the OLE field
         ' for the record set you are using:
         DisplayOleBitmap Picture1, Data1.Recordset("Photo")
      End If
      Screen.MousePointer = 0
   End Sub

Add the following to the Data2 Reposition event:

   Sub Data2_Reposition ()
      Screen.MousePointer = 11
      ' Make sure this is the current record:
      If Not (Data2.Recordset.EOF And Data2.Recordset.BOF) Then
         ' Change Photo to the name of the OLE field
         ' for the record set you are using:
         DisplayOleBitmap Picture2, Data2.Recordset("Photo")
      End If
      Screen.MousePointer = 0
   End Sub

From the Run menu, choose Start (ALT, R, S), or press the F5 key to run the program. Click the Data1 control; then click the Data2 control.

REFERENCES

In order to work around the 'Invalid Picture' error, the code in this article is based on the code published in the following article in the Microsoft Knowledge Base:

103115 PRB: Invalid Picture Error When Try to Bind Picture Control

Additional query words: 3.00

Keywords: kbprb KB113957

Microsoft KB Archive/113957

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