L_TwainFastAcquire2

Summary

Acquires image(s) from a TWAIN source and stores the image file(s) using Fast TWAIN feature.

Syntax

L_LTTWN_API L_INT L_TwainFastAcquire2(hSession, pszBaseFileName, nStartPageNumber, uFlags, uTransferMode, nFormat, nBitsPerPixel, bMultiPageFile, uUserBufSize, bUsePreferredBuffer, pfnCallBack, pUserData)

Parameters

HTWAINSESSION hSession

Handle to an existing TWAIN session. This handle is obtained by calling the L_TwainInitSession or L_TwainInitSession2 function.

L_TCHAR * pszBaseFileName

Character string containing the base name of the image file(s) in which to save the acquired data.

L_INT nStartPageNumber

The starting page number where the numbering of the newly scanned files names starts. For example, if this parameter has the value 3 then the scanned files will have the name "BaseFileName_0003.bmp".

Pass -1 for this parameter to start numbering files from page 1, which in this case for the first scanned file it will have the format "BaseFileName_0001.bmp".

L_UINT uFlags

Flag that indicates whether to display the manufacturer's user interface. You can combine values when appropriate by using a bitwise OR ( | ). The following are valid values:

L_UINT uTransferMode

Flag that indicates the transfer mode to be used when acquiring the image(s). Possible values are:

L_INT nFormat

Output file format. Valid values depend on the transfer mode used.

• For valid values for the File transfer mode, refer to the values for the uFileFormat member of the TRANSFEROPTIONS structure.
• For valid values for the Memory and Native transfer modes, refer to Formats of Output Files.

L_INT nBitsPerPixel

Resulting file's pixel depth. Note that not all bits per pixel are available to all file formats. If nBitsPerPixel is set to 0, the file will be stored using the closest BitsPerPixel value supported by that format.

L_BOOL bMultiPageFile

Flag that indicates whether to save multiple images into a single multipage file (if the output file format supports multipage files), or each page in a separate file. Possible values are:

L_UINT32 uUserBufSize

Specifies a user-defined buffer size. This value is valid only if uTransferMode is LTWAIN_BUFFER_MODE and bUsePreferredBuffer is FALSE. This value must be a multiple of 16.

L_BOOL bUsePreferredBuffer

Flag that indicates whether to use the user-defined buffer size or the Twain driver preferred buffer size. Possible values are:

LTWAINACQUIRECALLBACK pfnCallBack

Optional callback function, called twice for each page scan. The first call is to notify the page that the scanning has started, and the second call is to notify the page that the scanning has finished.

• If you do not provide a callback function, use NULL as the value of this parameter. No error reporting will occur.

• If you do provide a callback function, use the function pointer as the value of this parameter. The callback function must adhere to the function prototype described in the LTWAINACQUIRECALLBACK function.

L_VOID * pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs. To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure.

Returns

Comments

You may call L_TwainFindFastConfig before calling this function to retrieve the best scanning configuration in pOutBestConfig parameter, and then pass the values of the members in pOutBestConfig to this function.

This function was added in order to allow users to prevent already scanned files from being overwritten by a subsequent scan batch. This is accomplished by specifying the page number at which the newly created files should start. If, for example, three pages have been scanned in the first batch and the specified pszBaseFileName parameter was "BaseFileName.bmp", the output files will have the names "BaseFileName_0001.bmp", "BaseFileName_0002.bmp" and "BaseFileName_0003.bmp".

• If a new scan were started while continuing to use -1 for nStartPageNumber, the saved files would be overwritten. 

• In order to avoid overwriting files, pass a 4 for the nStartPageNumber parameter, so the newly scanned files will start from 4. The resulting files will save as "BaseFileName0004.bmp", "BaseFileName0005.bmp", ...etc.

If the file format specified in nFormat does not support multipage files, the value of bMultiPageFile will be ignored and the function will automatically save the acquired images in separate files. The naming of the files will be carried out as follows:

• If the string in pszBaseFileName is "Temp.jpg", the method will append the number of the image (0001, 0002, etc.), to the name of the file. Therefore, the output file names will be "Temp0001.jpg", "Temp0002.jpg", etc.

• Should more than 9,999 pages be acquired, numbering switches to using the actual page number. So after "Temp9999.jpg", the next page scanned would be named "Temp10000.jpg", and the following page would be "Temp10001.jpg", etc. After "Temp99999.jpg", the next page scanned would be named "Temp100000.jpg", and the following page would be "Temp100001.jpg", etc.

• If nStartPageNumber is not -1 (which should be any value bigger than zero), then the numbering will start from that value. So if, for example, the nStartPageNumber contains the value 4, then the output file names will be "Temp0004.jpg", "Temp0005.jpg", etc.

If the file format supports multipage files, this function will use the bMultiPageFile parameter to determine how to save multiple images.

• If bMultiPageFile is set to FALSE, each scanned page will be saved to a separate file, named in the same manner described in the paragraph above.

• If bMultiPageFile is TRUE, the name of the output file will be the exact string in pszBaseFileName "Temp.jpg" and it will be saved as a multipage file.

To cancel the acquire operation call the L_TwainCancelAcquire.

To stop acquire images only from the feeder of the TWAIN source, call the L_TwainStopFeeder function.

The LTWAIN_KEEPOPEN flag works only in the following cases:

1. Passed with LTWAIN_SHOW_USER_INTERFACE flag to make the TWAIN user-interface appear as a modeless dialog. The TWAIN data source remains open after scanning until the user closes it.

2. Passed with LTWAIN_SHOW_USER_INTERFACE and LTWAIN_MODAL_USER_INTERFACE flags to make the TWAIN user-interface appears as a modal dialog. The TWAIN data source remains open after scanning until the user closes it.

Required DLLs and Libraries

• LTTWN
• For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files to be Included with your Application.

See Also

Functions

• L_TwainFastAcquire
• L_TwainAcquire
• L_TwainAcquireList
• L_TwainInitSession
• L_TwainEndSession
• L_TwainOpenTemplateFile
• L_TwainCloseTemplateFile
• L_TwainTemplateDlg
• L_TwainAddCapabilityToFile
• L_TwainGetNumofCapsInFile
• L_TwainGetCapabilityFromFile
• L_TwainFindFastConfig
• L_TwainGetScanConfigs
• L_TwainFreeScanConfig
• L_TwainCancelAcquire
• L_TwainStopFeeder

Topics

• How to Acquire from the TWAIN Source
• TWAIN Functionality: Property Functions

Example

For complete sample, refer to FASTTWN
demo.

L_VOID EXT_CALLBACK FastAcquireCB(HTWAINSESSION hSession, 
                                  L_INT         nPage, 
                                  L_TCHAR*      pszFileName, 
                                  L_BOOL        bFinishScan, 
                                  L_VOID*       pUserData) 
{ 
   UNREFERENCED_PARAMETER(hSession); 
   UNREFERENCED_PARAMETER(pUserData); 
 
   L_TCHAR szTemp[MAX_PATH]; 
   if (bFinishScan) 
   { 
      wsprintf(szTemp, TEXT("The page # %d is scanned and saved to file name %s\n"), nPage, pszFileName); 
      MessageBox(NULL, szTemp, TEXT("Notice"), MB_OK); 
   } 
} 
 
L_INT TwainFastAcquire2Example(HWND hWnd,HTWAINSESSION hSession) 
{ 
   L_INT nRet; 
 
   nRet = L_TwainFastAcquire2(hSession, 
                             MAKE_IMAGE_PATH(TEXT("test.tif")), 
                             3, // start page number to use when numbering output file names, output files should be test_0003.tif, test_0004.tif, ...etc 
                             LTWAIN_SHOW_USER_INTERFACE, 
                             LTWAIN_BUFFER_MODE, 
                             FILE_TIF, 
                             1, 
                             TRUE, 
                             0,  
                             FALSE, 
                             FastAcquireCB, NULL); 
 
   if (nRet == SUCCESS) 
      MessageBox(hWnd, TEXT("Fast Twain function was successful"), TEXT("Notice"), MB_OK); 
   else 
      MessageBox(hWnd, TEXT("Error occurred during fast Twain function!!!"), TEXT("Error!!!"), MB_OK); 
 
   return nRet; 
}