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.NET TWAIN image scanner

, 12 May 2002 Public Domain
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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

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About the Author

NETMaster
Web Developer
Switzerland Switzerland
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Comments and Discussions

 
GeneralRe: Twain Driver Interface Dialog Pin
Imanol Pinto Lopez at 29-May-14 0:18
memberImanol Pinto Lopez29-May-14 0:18 
GeneralRe: Twain Driver Interface Dialog Pin
KB.Rajesh at 24-Feb-15 22:31
memberKB.Rajesh24-Feb-15 22:31 
GeneralRe: Twain Driver Interface Dialog Pin
KB.Rajesh at 24-Feb-15 22:29
memberKB.Rajesh24-Feb-15 22:29 
QuestionAbout disabling Scan Property form Pin
Member 10717941 at 7-Apr-14 3:22
memberMember 107179417-Apr-14 3:22 
AnswerRe: About disabling Scan Property form Pin
danajp_59 at 5-May-14 12:23
memberdanajp_595-May-14 12:23 
QuestionGreat Pin
magicyangjay at 18-Mar-14 22:50
membermagicyangjay18-Mar-14 22:50 
QuestionGet supported capabilities Pin
M.Azadi at 9-Mar-14 23:15
memberM.Azadi9-Mar-14 23:15 
QuestionWindows 8 errors with TwainLib.Twain.DSMident Pin
pserrao at 5-Mar-14 4:57
memberpserrao5-Mar-14 4:57 
AnswerRe: Windows 8 errors with TwainLib.Twain.DSMident Pin
Ravishankar chinnur at 5-Mar-14 19:12
memberRavishankar chinnur5-Mar-14 19:12 
GeneralRe: Windows 8 errors with TwainLib.Twain.DSMident Pin
pserrao at 6-Mar-14 10:37
memberpserrao6-Mar-14 10:37 
GeneralRe: Windows 8 errors with TwainLib.Twain.DSMident Pin
Ravishankar chinnur at 6-Mar-14 19:13
memberRavishankar chinnur6-Mar-14 19:13 
GeneralRe: Windows 8 errors with TwainLib.Twain.DSMident Pin
smile8691 at 15-Dec-14 6:54
membersmile869115-Dec-14 6:54 
Questionscanning one after another is not posiible Pin
Ravishankar chinnur at 5-Mar-14 3:08
memberRavishankar chinnur5-Mar-14 3:08 
AnswerRe: scanning one after another is not posiible Pin
malcolmxu at 21-Mar-14 6:54
membermalcolmxu21-Mar-14 6:54 
AnswerRe: scanning one after another is not posiible Pin
Antriksh Patel at 27-Jul-14 19:12
memberAntriksh Patel27-Jul-14 19:12 
BugInsufficient Memory Pin
keencoder at 20-Jan-14 23:42
memberkeencoder20-Jan-14 23:42 
GeneralRe: Insufficient Memory Pin
Member 10354796 at 22-Sep-14 23:13
memberMember 1035479622-Sep-14 23:13 
QuestionHow to scan on both sides of the document Pin
sandeep758 at 7-Jan-14 22:58
membersandeep7587-Jan-14 22:58 
Questionsave images Pin
ezelden.sahi at 12-Nov-13 22:30
memberezelden.sahi12-Nov-13 22:30 
QuestionHow can i change the transfer mode to File Pin
Murugan Kolanji at 11-Nov-13 3:43
memberMurugan Kolanji11-Nov-13 3:43 
GeneralThank you so much~! Pin
Cheon sang at 10-Nov-13 23:03
memberCheon sang10-Nov-13 23:03 
Question.NET TWAIN image scanner Convert to for VB 2010 Pin
Dibakar Mishra at 30-Oct-13 4:55
memberDibakar Mishra30-Oct-13 4:55 
QuestionGdipSaveImageToStream brings back a empty stream Pin
Member 3913283 at 23-Oct-13 9:49
memberMember 391328323-Oct-13 9:49 
GeneralMy vote of 5 Pin
Lucas Lima Araujo at 27-Sep-13 7:37
memberLucas Lima Araujo27-Sep-13 7:37 
QuestionWindows 8 Fails Pin
Lucas Lima Araujo at 27-Sep-13 5:39
memberLucas Lima Araujo27-Sep-13 5:39 
AnswerRe: Windows 8 Fails Pin
blastnsmash at 10-Dec-13 7:59
memberblastnsmash10-Dec-13 7:59 
GeneralRe: Windows 8 Fails Pin
smile8691 at 28-Jan-14 8:37
membersmile869128-Jan-14 8:37 
AnswerRe: Windows 8 Fails Pin
blastnsmash at 10-Dec-13 10:10
memberblastnsmash10-Dec-13 10:10 
Questionsave in Db Pin
partia at 3-Sep-13 4:16
memberpartia3-Sep-13 4:16 
AnswerRe: save in Db Pin
Windy Liu at 13-Sep-13 1:05
memberWindy Liu13-Sep-13 1:05 
GeneralRe: save in Db Pin
partia at 20-Sep-13 4:31
memberpartia20-Sep-13 4:31 
GeneralRe: save in Db Pin
Windy Liu at 21-Sep-13 22:23
memberWindy Liu21-Sep-13 22:23 
QuestionPage rotation Pin
Ricardo Valero at 29-Aug-13 3:11
memberRicardo Valero29-Aug-13 3:11 
QuestionTWAIN Pin
Member 10189285 at 25-Aug-13 17:33
memberMember 1018928525-Aug-13 17:33 
AnswerRe: TWAIN Pin
p312ry at 3-Dec-13 16:41
memberp312ry3-Dec-13 16:41 
Questionusing TWAIN Kyocera FS-1035 [modified] Pin
Member 9988236 at 14-Aug-13 1:48
memberMember 998823614-Aug-13 1:48 
QuestionPass parameters to without using ui Pin
saijagadeesh at 30-Jul-13 4:13
membersaijagadeesh30-Jul-13 4:13 
GeneralMy vote of 5 Pin
shiva_19 at 4-Jul-13 20:30
membershiva_194-Jul-13 20:30 
Questiontwain scanning in vb.net Pin
Dina_Du at 27-Jun-13 19:26
memberDina_Du27-Jun-13 19:26 
Questionc# n vb Pin
Imam Azinuddin at 19-Jun-13 20:14
memberImam Azinuddin19-Jun-13 20:14 
QuestionError in the Code Pin
Herman M. Reyes at 7-Jun-13 1:44
memberHerman M. Reyes7-Jun-13 1:44 
AnswerRe: Error in the Code Pin
Member 10158694 at 16-Jul-13 11:14
memberMember 1015869416-Jul-13 11:14 
GeneralRe: Error in the Code Pin
Herman M. Reyes at 26-Jul-13 2:06
memberHerman M. Reyes26-Jul-13 2:06 
GeneralRe: Error in the Code Pin
Member 10204633 at 11-Sep-13 10:19
memberMember 1020463311-Sep-13 10:19 
Questionthanks Pin
Member 7863913 at 22-May-13 13:15
memberMember 786391322-May-13 13:15 
QuestionHow can i scan multi pages Pin
Member 3973267 at 19-May-13 18:33
memberMember 397326719-May-13 18:33 
QuestionNeed help to fix Issue in Twain .net Library Pin
vinaykn.rao at 22-Apr-13 4:07
membervinaykn.rao22-Apr-13 4:07 
QuestionException throws when I use in Win7 64 bit Pin
anisfathima at 18-Apr-13 23:11
memberanisfathima18-Apr-13 23:11 
AnswerRe: Exception throws when I use in Win7 64 bit Pin
Jnnxp at 5-Aug-13 17:11
memberJnnxp5-Aug-13 17:11 
Questionhow set Image info Pin
Mohamed Nabawy at 15-Apr-13 7:59
memberMohamed Nabawy15-Apr-13 7:59 

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