Acquiring an Image (Visual Basic)

Take the following steps to start a project and to add some code that acquires an image from a TWAIN source:

1.	Start Visual Basic.
2.	Add the LEAD RasterView Control to your project. On the Project pull-down menu, use the Components option, and select the LEAD Raster View Control (14.5).
3.	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 (14.5).
	On the Project pull-down menu, use the References option, and select the LEAD Raster Variant Object Library (14.5).
4.	Add the following code to the general declarations section of your project:

Public TwainCap As New LEADTwainCapability
Public WithEvents RasterTwain As LEADRasterTwain
Public nXferMode As Integer
Public nRet As Integer

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

Set RasterTwain = New LEADRasterTwain
RasterTwain.InitSession hWnd

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

RasterTwain.EndSession

7.	At the top of your main form, add six Command Buttons and three Option Buttons and name them as follows:
	Name	Caption
	OK	OK
	Cancel	Cancel
	Acquire	Acquire
	SelectSource	SelectSource
	CmdSaveTemplate	Save Template File
	Native	Native
	MemBuf	Memory Buffered
	File	File
	CmdLoadTemplate	Load Template File
8.	Code the OK 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 OK_Click()
Unload Me
End Sub

9.	Code the Cancel 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 Cancel_Click()
Unload Me
End Sub

10.	Code the Acquire control's Click procedure as follows:

Private Sub Acquire_Click()
RasterTwain.Acquire L_LTWAIN_SHOW_USER_INTERFACE
End Sub

11.	Code the SelectSource control's Click procedure as follows:

Private Sub SelectSource_Click()
RasterTwain.SelectSource
End Sub

12.	Code the CmdSaveTemplate control's Click procedure as follows:

Private Sub cmdSaveTemplate_Click()
nRet = RasterTwain.SaveTemplate("c:\test.ltt")
End Sub

13.	Code the cmdLoadTemplate control's Click procedure as follows:

Private Sub cmdLoadTemplate_Click()
nRet = RasterTwain.LoadTemplate("c:\test.ltt")
End Sub

14.	Code the Native option control's Click procedure as Follows:

Private Sub Native_Click()
   Dim CapVal As LEADRasterVariant
   nXferMode = L_TWSX_NATIVE

   CapVal.Type = VALUE_USHORT
   CapVal.LongValue = nXferMode
   TwainSetCapability L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16
End Sub

15.	Code the MemBuf Option control's Click procedure as follows:

Private Sub MemBuf_Click()
Dim CapVal As LEADRasterVariant
   nXferMode = L_TWSX_MEMORY
   CapVal.Type = VALUE_USHORT
   CapVal.LongValue = nXferMode
   TwainSetCapability L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16
End Sub

16.	Code the File Option control's Click procedure as follows:

Private Sub File_Click()
Dim CapVal As LEADRasterVariant
   nXferMode = L_TWSX_FILE
   CapVal.Type = VALUE_USHORT
   CapVal.LongValue = nXferMode
   TwainSetCapability L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16
   RasterTwain.FileTransferName = "c:\twain.bmp"
End Sub

17.	Code RasterTwain object’s procedure as follows:

Private Sub RasterTwain_AcquirePageEvent(ByVal pBitmap As Long)
MsgBox "Acquisition of Image Done"
LEADRasterView1.Raster. InsertBitmapListItem -1, pBitmap
End Sub

18.	Add this Function to the Project:

Public Function TwainSetCapability(uCapability As Integer, CapVal As LEADRasterVariant, uItemType As Integer) As Integer
   Dim iRet As Integer

   TwainCap.EnableMethodErrors = False
   TwainCap.CapInfo.Capability = uCapability
   TwainCap.CapInfo.ConType = L_TWON_ONEVALUE
   TwainCap.CapOneValue.OneValItemType = uItemType
   TwainCap.CapOneValue.OneValCapValue = CapVal

   iRet = RasterTwain.SetCapability2(TwainCap, L_LTWAIN_CAPABILITY_SET)
   TwainSetCapability = iRet
End Function

19.	Run your program to test it.