Twain Capabilities – Using CAP_SUPPORTEDCAPS

[si_ben]

Hey there, new to Twain Development.

I have been working on a project for work for a few months. Created this awesome class to do scanning with WIA and found that most of our customers use Scanner devices that use TWAIN.

I have attempted to futz around with twain. I got selecting a source and acquiring an image converted from C# TwainGUI example. I code in Visual Basic so converted most of it. Now what I’m trying to do is create an application that lists the capabilities of the Source. I guess I still am not fully understanding how to access the TW_ARRAY.

'// This is my structure for Capability
_
Friend Class TwCapability
'Declare Vars
Public Cap As Short
Public ConType As Short
Public Handle As IntPtr
' TW_CAPABILITY
Public Sub New(ByVal cap__1 As TwCap)
Cap = CShort(cap__1)
ConType = -1
End Sub
Public Sub New(ByVal cap__1 As TwCap, ByVal sval As Short)
Cap = CShort(cap__1)
ConType = CShort(TwOn.One)
Handle = Twain.GlobalAlloc(&H42, 6)
Dim pv As IntPtr = Twain.GlobalLock(Handle)
Marshal.WriteInt16(pv, 0, CShort(TwType.Int16))
Marshal.WriteInt32(pv, 2, CInt(sval))
Twain.GlobalUnlock(Handle)
End Sub
Protected Overrides Sub Finalize()
Try
If Handle <> IntPtr.Zero Then
Twain.GlobalFree(Handle)
End If
Finally
MyBase.Finalize()
End Try
End Sub
End Class


'// This is my Enum
Friend Enum TwCap As Short
' CAP_XFERCOUNT
XferCount = &H1
SupportedCaps = &H1005 '// This is what I added
' ICAP_...
ICompression = &H100
IPixelType = &H101
IUnits = &H102
IXferMech = &H103
End Enum


'// This is my function
Public Function Load_DS_SupportedCapabilities()
Dim rc As TwRC
Dim cc As TwCC
Dim cap As New TwCapability(TwCap.SupportedCaps)
rc = DScap(appid, srcds, TwDG.Control, TwOn.Range, TwMSG.Get, cap)
If rc <> TwRC.Success Then
cc = DScap(appid, srcds, TwDG.Control, TwOn.Range, TwMSG.Get, cap)
If (cc <> TwCC.Success) Then
Select Case cc.ToString()
Case Is = "Bummer"
MessageBox.Show("General Failure: Unload Source Immediately!")
Case Else
MessageBox.Show("Unkown Error: Unload Source Immediately!")
End Select
End If
Else

End If
Return "Success"
End Function


I attempt calling this function when I am in State 4. I have just been really lost and I feel like I am getting nowhere after 2 weeks.

Any comments or suggestions would be really helpful. Even pointing me in the right direction in the Spec Book (PDF) would be nice. Thank you.

[si_ben]

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