Click here to Skip to main content
11,709,537 members (53,065 online)
Click here to Skip to main content

.NET TWAIN image scanner

, 12 May 2002 Public Domain 3.1M 86.1K 402
Rate this:
Please Sign up or sign in to vote.
Using TWAIN API to scan images

Sample Screenshot

Abstract

In Windows imaging applications, the most used API for scanning is TWAIN www.twain.org. Unfortunately, the new .NET Framework has no built-in support for TWAIN. So we have to work with the interop methods of .NET to access this API. This article doesn't explain this interop techniques, and good knowledge of the TWAIN 1.9 specifications is assumed! The sample code included doesn't present a finished library, only some essential steps for a minimal TWAIN adaption to .NET applications.

Details

First step was to port the most important parts of TWAIN.H, these are found in TwainDefs.cs. The real logic for calling TWAIN is coded in the class Twain, in file TwainLib.cs.. As the TWAIN API is exposed by the Windows DLL, twain_32.dll, we have to use the .NET DllImport mechanism for interop with legacy code. This DLL has the central DSM_Entry(), ordinal #1 function exported as the entry point to TWAIN. This call has numerous parameters, and the last one is of variable type! It was found to be best if we declare multiple variants of the call like:

[DllImport("twain_32.dll", EntryPoint="#1")]
private static extern TwRC DSMparent(
    [In, Out] TwIdentity origin,
    IntPtr zeroptr,
    TwDG dg, TwDAT dat, TwMSG msg,
    ref IntPtr refptr );

The Twain class has a simple 5-step interface:

class Twain
{
    Init();
    Select();
    Acquire();
    PassMessage();
    TransferPictures();
}

For some sort of 'callbacks', TWAIN uses special Windows messages, and these must be caught from the application-message-loop. In .NET, the only way found was IMessageFilter.PreFilterMessage(), and this filter has to be activated with a call like Application.AddMessageFilter(). Within the filter method, we have to forward each message to Twain.PassMessage(), and we get a hint (enum TwainCommand) back for how we have to react.

Sample App

The sample is a Windows Forms MDI-style application. It has the two TWAIN-related menu items Select Source... and Acquire... Once an image is scanned in, we can save it to a file in any of the GDI+ supported file formats (BMP, GIF, TIFF, JPEG...)

Limitations

All code was only tested on Windows 2000SP2, with an Epson Perfection USB scanner and an Olympus digital photo camera. The scanned picture is (by TWAIN spec) a Windows DIB, and the sample code has VERY little checking against error return codes and bitmap formats. Unfortunately, no direct method is available in .NET to convert a DIB to the managed Bitmap class... Some known problems may show up with color palettes and menus.

Note, TWAIN has it's root in 16-Bit Windows! For a more modern API supported on Windows ME/XP, have a look at Windows Image Acquisition (WIA).

License

This article, along with any associated source code and files, is licensed under A Public Domain dedication

Share

About the Author

NETMaster
Web Developer
Switzerland Switzerland
No Biography provided

You may also be interested in...

Comments and Discussions

 
QuestionError in the Code Pin
Herman M. Reyes7-Jun-13 0:44
memberHerman M. Reyes7-Jun-13 0:44 
AnswerRe: Error in the Code Pin
Member 1015869416-Jul-13 10:14
memberMember 1015869416-Jul-13 10:14 
GeneralRe: Error in the Code Pin
Herman M. Reyes26-Jul-13 1:06
memberHerman M. Reyes26-Jul-13 1:06 
GeneralRe: Error in the Code Pin
Member 1020463311-Sep-13 9:19
memberMember 1020463311-Sep-13 9:19 
Questionthanks Pin
Member 786391322-May-13 12:15
memberMember 786391322-May-13 12:15 
QuestionHow can i scan multi pages Pin
Member 397326719-May-13 17:33
memberMember 397326719-May-13 17:33 
QuestionNeed help to fix Issue in Twain .net Library Pin
vinaykn.rao22-Apr-13 3:07
membervinaykn.rao22-Apr-13 3:07 
QuestionException throws when I use in Win7 64 bit Pin
anisfathima18-Apr-13 22:11
memberanisfathima18-Apr-13 22:11 
Hi guys.

It works great in Windows XP whereas in Win 7 64 bit it throws an error below.

Unable to load DLL 'twain_32.dll': The device is not ready. (Exception from HRESULT: 0x80070015)

Please help me guys. That will be really appreciated.

Thanks,
Raja.S
AnswerRe: Exception throws when I use in Win7 64 bit Pin
Jnnxp5-Aug-13 16:11
memberJnnxp5-Aug-13 16:11 
Questionhow set Image info Pin
Mohamed Nabawy15-Apr-13 6:59
memberMohamed Nabawy15-Apr-13 6:59 
QuestionScanner Error Pin
asheykh14-Apr-13 22:05
memberasheykh14-Apr-13 22:05 
QuestionTwainCommand.TransferReady: hbitmap to gdi+ bitmap Pin
liuxu093826-Mar-13 21:21
memberliuxu093826-Mar-13 21:21 
QuestionThe "twaingui_demo.zip" is damaged? Pin
liuxu093826-Mar-13 0:16
memberliuxu093826-Mar-13 0:16 
QuestionScanning on Win7 64Bit Pin
khalilsa27-Feb-13 4:19
memberkhalilsa27-Feb-13 4:19 
AnswerRe: Scanning on Win7 64Bit Pin
ricardofrias20-Mar-13 7:48
memberricardofrias20-Mar-13 7:48 
AnswerRe: Scanning on Win7 64Bit Pin
Jnnxp5-Aug-13 16:12
memberJnnxp5-Aug-13 16:12 
QuestionWIA driver is not working with multiple pages Pin
anisfathima9-Jan-13 22:59
memberanisfathima9-Jan-13 22:59 
AnswerRe: WIA driver is not working with multiple pages Pin
smile869114-Feb-13 8:51
membersmile869114-Feb-13 8:51 
Bughow set boolean value CAP_PAPERDETECTABLE,ICAP_AUTOMATICDESKEW ecc..? Pin
nturri13065-Jan-13 5:07
membernturri13065-Jan-13 5:07 
QuestionNeed help Pin
Member 806548423-Nov-12 17:54
memberMember 806548423-Nov-12 17:54 
AnswerRe: Need help Pin
Abdullah Çetinkaya22-Jan-13 23:11
memberAbdullah Çetinkaya22-Jan-13 23:11 
Questionget error in multipage scanning Pin
yuee17-Nov-12 2:08
memberyuee17-Nov-12 2:08 
AnswerRe: get error in multipage scanning Pin
smile86917-Nov-12 2:09
membersmile86917-Nov-12 2:09 
Questionhelp Pin
bijarcity24-Oct-12 6:09
memberbijarcity24-Oct-12 6:09 
AnswerRe: help Pin
smile86911-Nov-12 5:34
membersmile86911-Nov-12 5:34 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web02 | 2.8.150819.1 | Last Updated 13 May 2002
Article Copyright 2001 by NETMaster
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid