Twain Feeder: Tutorial #2 (Visual Basic)

Take the following steps to start a project and to add some code that acquires the images using Fast Twain:

1.	Start Visual Basic.
2.	Add the LEAD RasterTwain Object Library and LEAD Raster Variant Object Library to your project.
	On the Project pull-down menu, use the References option, and select the LEAD RasterTwain Object Library.
	On the Project pull-down menu, use the References option, and select the LEAD Raster Variant Object Library.
3.	Add the following code to the general declarations section of your project:

Public TwainCap As New LEADTwainCapability_U
Public WithEvents RasterTwain As LEADRasterTwain_U

4.	Add the following code to the main form's Load procedure:

Set RasterTwain = New LEADRasterTwain_U
RasterTwain.InitSession hWnd
RasterTwain.EnableMethodErrors = False

5.	Add the following code to the main form's Unload procedure:

RasterTwain.EndSession

6.	Add the following button:
	Name	Caption
	cmdAcquire	Acquire
7.	Code the Acquire control's Click procedure as follows. In online help, you can use the Edit pull-down menu to copy the block of code.

Private Sub cmdAcquire_Click()
   Dim nRet As Integer
   Dim bEnable As Boolean

   RasterTwain.SelectSource

   TwainCap.CapInfo.Capability = L_CAP_FEEDERENABLED
   TwainCap.CapInfo.ConType = L_TWON_ONEVALUE

   bEnable = True
   Dim RasVar As New LEADRasterVariant_U
   RasVar. = VALUE_BOOLEAN
   RasVar. = bEnable

   TwainCap.CapOneValue.OneValItemType = L_TWTY_BOOL
   TwainCap.CapOneValue.OneValCapValue = RasVar

   nRet = RasterTwain.SetCapability2(TwainCap, L_LTWAIN_CAPABILITY_SET)
   If nRet = 0 Then
      MsgBox "CAP_FEEDERENABLED capability is enabled"

      ' check if there is document loaded in the feeder
      TwainCap.CapInfo.Capability = L_CAP_DUPLEX
      TwainCap.CapInfo.ConType = L_TWON_ONEVALUE

      nRet = RasterTwain.GetCapability2 (TwainCap, L_LTWAIN_CAPABILITY_GETVALUES)
      If nRet = 0 Then
         ' check if the selected driver supports duplex capability
         bEnable = TwainCap.CapOneValue.OneValCapValue.BooleanValue
         If bEnable Then
            MsgBox "There is document loaded in the feeder"
         Else
            MsgBox "There is no document loaded in the feeder"
         End If
      End If
   Else
      MsgBox "Can't enable AutoFeed capability"
   End If

   ' try to acquire pages using CAP_FEEDERENABLED and CAP_FEEDERLOADED capabilities
   RasterTwain.Acquire L_LTWAIN_SHOW_USER_INTERFACE Or L_LTWAIN_MODAL_USER_INTERFACE
End Sub