Set up a TWAIN Duplex (Dual Page) Scan

Note: The purpose of this TWAIN tutorial is to provide you a quick and easy way to generate a TWAIN program. For more in depth TWAIN programming, refer to the TWAIN demo.

To create and run a program that implements LEADTOOLS TWAIN Duplex features:

1.	Create a new directory in the Examples\CDLL directory called TwainDuplex
2.	Copy everything in the SimpleLoad directory into the TwainDuplex directory.
3.	Compile the project as it is and run SimpleLoad.exe to familiarize yourself with the basic program.
4.	In the Imports.cpp, add the following lines:

#if defined(WIN64) 
#else 
   #pragma comment(lib, "..\\..\\..\\Lib"L_VER_DESIGNATOR"\\CDLL\\Win32\\Lttwn_u.lib") 
#endif // #if defined(WIN64)

5.	Add the following line in StdAfx.h in the TwainDuplex directory:

#include "..\..\..\include\lttwn.h"

6.	Define the following global variables in Ezfunc.h in the TwainDuplex directory:

HTWAINSESSION hSession; 
  
Also, add the following defines: 
  
#define IDM_ACQUIRE        200

7.	Edit EZFUNC.RC file in the TwainCap directory and add the following lines:

#include "EZFUNC.H" 
  
MAIN_MENU   MENU 
BEGIN 
   MENUITEM "Acquire"         IDM_ACQUIRE 
END

8.	In the InitApplication function change the line:

wcWindowClass.lpszMenuName = NULL;  /* No menu */   
to be   
wcWindowClass.lpszMenuName = TEXT("MAIN_MENU");

9.	In the MainWndProc function and before the handling of the WM_PALETTECHANGED message add the following code:

case WM_COMMAND: 
{ 
   switch (LOWORD(wParam)) 
   { 
      case IDM_ACQUIRE: 
      { 
      } 
      break; 
   } 
} 
break;

10.	In the IDM_ACQUIRE menu handler add the following code:

case IDM_ACQUIRE: 
{ 
   TwainTestDuplex(hWnd); 
}

11.	Add the following function to the EZFUNC.CPP:

L_INT EXT_CALLBACK TwainAcquireCB(HTWAINSESSION hSession, pBITMAPHANDLE pBitmap, L_VOID * pUserData) 
{ 
   UNREFERENCED_PARAMETER(hSession); 
   UNREFERENCED_PARAMETER(pBitmap); 
   UNREFERENCED_PARAMETER(pUserData); 
    
   if (LeadBitmap.Flags.Allocated) 
      L_FreeBitmap(&LeadBitmap); 
    
   L_CopyBitmap(&LeadBitmap, pBitmap, sizeof(BITMAPHANDLE)); 
   L_FreeBitmap(pBitmap); 
   return SUCCESS; 
}

12.	Add the following function to the EZFUNC.CPP after the TwainAcquireCB function:

void TwainTestDuplex(HWND hWnd) 
{ 
   HTWAINSESSION hSession; 
   APPLICATIONDATA AppData; 
   L_INT nRet; 
   TW_CAPABILITY twCap; 
   memset(&AppData, 0, sizeof(APPLICATIONDATA)); 
   AppData.hWnd = hWnd; 
   lstrcpy (AppData.szManufacturerName, TEXT("LEAD Technologies, Inc.")); 
   lstrcpy (AppData.szAppProductFamily, TEXT("LEAD Sample")); 
   lstrcpy (AppData.szVersionInfo,      TEXT("Version 1.0")); 
   lstrcpy (AppData.szAppName,          TEXT("LEAD Sample")); 
   AppData.uStructSize = sizeof(APPLICATIONDATA); 
   nRet = L_TwainInitSession(&hSession, &AppData); 
   if (nRet != TWAIN_SUCCESS) 
      return; 
   L_TwainSelectSource(hSession, NULL); 
   L_TwainStartCapsNeg(hSession); 
   twCap.Cap = CAP_DUPLEX; 
   twCap.ConType = TWON_ONEVALUE; 
   twCap.hContainer = NULL; 
   nRet = L_TwainGetCapability(hSession, &twCap, LTWAIN_CAPABILITY_GETVALUES); 
   if (nRet == TWAIN_SUCCESS) 
   { 
      // check if the selected driver supports duplex capability 
      pTW_ONEVALUE pOneValue = (pTW_ONEVALUE)GlobalLock(twCap.hContainer); 
      if (pOneValue->ItemType != TWTY_UINT16) 
      { 
         GlobalUnlock(twCap.hContainer); 
         L_TwainFreeContainer(&twCap); 
         L_TwainEndCapsNeg(hSession); 
         L_TwainEndSession(&hSession); 
         return; 
      } 
      TW_UINT16 item = (TW_UINT16)pOneValue->Item; 
      switch (item) 
      { 
         case TWDX_NONE: 
         MessageBox(hWnd, TEXT("Duplex capability is not supported in the selected driver"), TEXT("Notice"), MB_OK); 
         break; 
         case TWDX_1PASSDUPLEX: 
         MessageBox(hWnd, TEXT("1 Pass Duplex capability is supported in the selected driver"), TEXT("Notice"), MB_OK); 
         break; 
         case TWDX_2PASSDUPLEX: 
         MessageBox(hWnd, TEXT("2 Pass Duplex capability is supported in the selected driver"), TEXT("Notice"), MB_OK); 
         break; 
      } 
      GlobalUnlock(twCap.hContainer); 
      L_TwainFreeContainer(&twCap); 
      // make sure the duplex capability is enabled 
      if (item != TWDX_NONE) 
      { 
         BOOL bEnable = TRUE; 
         twCap.Cap = CAP_DUPLEXENABLED; 
         twCap.ConType = TWON_ONEVALUE; 
         twCap.hContainer = GlobalAlloc(GHND, sizeof(TW_ONEVALUE)); 
         pTW_ONEVALUE pOneValue = (pTW_ONEVALUE)GlobalLock(twCap.hContainer); 
         pOneValue->ItemType = TWTY_BOOL; 
         pOneValue->Item = (TW_UINT32)bEnable; 
         GlobalUnlock(twCap.hContainer); 
         nRet = L_TwainSetCapability(hSession, &twCap, LTWAIN_CAPABILITY_SET); 
         if (nRet == TWAIN_SUCCESS) 
            MessageBox(hWnd, TEXT("The duplex capability is enabled"), TEXT("Notice"), MB_OK); 
         else 
            MessageBox(hWnd, TEXT("Can't enable duplex capability"), TEXT("Notice"), MB_OK); 
      } 
   } 
   else 
      MessageBox(hWnd, TEXT("Duplex capability is not supported in the selected driver"), TEXT("Notice"), MB_OK); 
   L_TwainEndCapsNeg(hSession); 
   // try to acquire pages using duplex capability 
   L_TwainAcquire(hSession, NULL, sizeof(BITMAPHANDLE), TwainAcquireCB, LTWAIN_SHOW_USER_INTERFACE | LTWAIN_MODAL_USER_INTERFACE, NULL, NULL); 
   L_TwainEndSession(&hSession); 
}

13.	Compile and test the program.

Help Version 19.0.2017.10.27

LEADTOOLS TWAIN C API Help

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