Camera vs Scanner Question

Hello,

We have an app written in VB 6 and LT 14. We can scan, set X & Y resolution, Show UI, tell if its a feeder or flatbed scanner. How can we tell if the device is a camera or a scanner? We do not want to check for X/Y resolution or feeder/flatbed capabilities if it is a camera.

Also, we do not understand the RasterTwain.QueryCapabilty command. Could you enclose a code snippet that demonstrates that function? We could not tell from the help file how it works.
Thanks!

Although scanners and cameras are the most common types of Twain devices, they are not necessarily the only types. Furthermore, the capabilities present in both types of devices overlap, meaning there could be many capabilities common to both.
You could make use of the fact that ICAP_UNITS is required by all types of sources, and that cameras almost always support only the PIXELS unit, while most if not all scanners support the INCHES unit.

I tried the following code with 4 different Twain drivers (1 camera and 3 scanners) and it worked. However, there's no guarantee it will always work, because you can never know how different vendors write their Twain drivers.

Sub CheckTwainDeviceType()
   Dim var As New LEADRasterVariant
   Dim TwainCap As New LEADTwainCapability_D ' or LEADTwainCapability
   Set RasTwain = New LEADRasterTwain_D ' or LEADRasterTwain
   RasTwain.InitSession Me.hWnd
   
   RasTwain.SelectSource
   TwainCap.CapInfo.ConType = L_TWON_ONEVALUE
   TwainCap.CapInfo.Capability = L_ICAP_UNITS
   TwainCap.EnableMethodErrors = False
   
   var.Type = VALUE_USHORT
   var.LongValue = L_TWUN_INCHES
   TwainCap.CapOneValue.OneValItemType = L_TWTY_UINT16
   TwainCap.CapOneValue.OneValCapValue = var
   RasTwain.EnableMethodErrors = False
   Dim nRet As Integer
   nRet = RasTwain.SetCapability2(TwainCap, L_LTWAIN_CAPABILITY_SET)
   If 0 = nRet Then 'success
      MsgBox "Most likely a scanner"
   Else
      MsgBox "Most likely a camera"
   End If
   Set TwainCap = Nothing
   Set var = Nothing
   RasTwain.EndSession
End Sub


About the Query Capability method, here's a code sample that uses it. If you want to perform the same check using it, the camera will have TwainCap.CapEnum.EnumNumOfItems equal to 1, and TwainCap.CapEnum.EnumCapValue(0).LongValue equal to 5 (L_TWUN_PIXELS):

Sub TwainQueryCap()
   Dim var As New LEADRasterVariant
   Dim TwainCap As New LEADTwainCapability_D ' or LEADTwainCapability
   Set RasTwain = New LEADRasterTwain_D ' or LEADRasterTwain
   RasTwain.InitSession Me.hWnd
   
   RasTwain.SelectSource
   TwainCap.CapInfo.ConType = L_TWON_ENUMERATION
   TwainCap.CapInfo.Capability = L_ICAP_UNITS
   TwainCap.EnableMethodErrors = False
   
   RasTwain.EnableMethodErrors = False
   Dim nRet As Integer
   nRet = RasTwain.QueryCapability2(TwainCap)
   Dim msg As String, i As Integer
   If 0 = nRet Then 'success
      msg = "Num of values = " & TwainCap.CapEnum.EnumNumOfItems & vbCrLf
      For i = 0 To TwainCap.CapEnum.EnumNumOfItems - 1
         msg = msg & "value " & i & " is " & TwainCap.CapEnum.EnumCapValue(i).LongValue & vbCrLf
      Next
      MsgBox msg
   End If
   Set TwainCap = Nothing
   Set var = Nothing
   RasTwain.EndSession
End Sub