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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

 
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 
QuestionScanner Error Pin
asheykh at 14-Apr-13 23:05
memberasheykh14-Apr-13 23:05 
QuestionTwainCommand.TransferReady: hbitmap to gdi+ bitmap Pin
liuxu0938 at 26-Mar-13 22:21
memberliuxu093826-Mar-13 22:21 
QuestionThe "twaingui_demo.zip" is damaged? Pin
liuxu0938 at 26-Mar-13 1:16
memberliuxu093826-Mar-13 1:16 
QuestionScanning on Win7 64Bit Pin
khalilsa at 27-Feb-13 5:19
memberkhalilsa27-Feb-13 5:19 
AnswerRe: Scanning on Win7 64Bit Pin
ricardofrias at 20-Mar-13 8:48
memberricardofrias20-Mar-13 8:48 
AnswerRe: Scanning on Win7 64Bit Pin
Jnnxp at 5-Aug-13 17:12
memberJnnxp5-Aug-13 17:12 
Questionuse in asp.net? Pin
Kalpana Volety at 11-Jan-13 10:59
memberKalpana Volety11-Jan-13 10:59 
AnswerRe: use in asp.net? Pin
Jnnxp at 5-Aug-13 17:17
memberJnnxp5-Aug-13 17:17 
QuestionWIA driver is not working with multiple pages Pin
anisfathima at 9-Jan-13 23:59
memberanisfathima9-Jan-13 23:59 
Hi all ,

I am a .net developer , i have got an issue with WIA driver. I am able to scan single page with WIA driver ,however I am not able to scann multiple pages with WIA driver.

I have gone throw the Twain software site they told that this code will be work for twain and WIA drivers

Can you give me the suggestion please?

thanks
AnswerRe: WIA driver is not working with multiple pages Pin
smile8691 at 14-Feb-13 9:51
membersmile869114-Feb-13 9:51 
Bughow set boolean value CAP_PAPERDETECTABLE,ICAP_AUTOMATICDESKEW ecc..? Pin
nturri1306 at 5-Jan-13 6:07
membernturri13065-Jan-13 6:07 
QuestionNeed help Pin
Member 8065484 at 23-Nov-12 18:54
memberMember 806548423-Nov-12 18:54 
AnswerRe: Need help Pin
Abdullah Çetinkaya at 23-Jan-13 0:11
memberAbdullah Çetinkaya23-Jan-13 0:11 
Questionget error in multipage scanning Pin
yuee1 at 7-Nov-12 3:08
memberyuee17-Nov-12 3:08 
AnswerRe: get error in multipage scanning Pin
smile8691 at 7-Nov-12 3:09
membersmile86917-Nov-12 3:09 
Questionhelp Pin
bijarcity at 24-Oct-12 7:09
memberbijarcity24-Oct-12 7:09 
AnswerRe: help Pin
smile8691 at 1-Nov-12 6:34
membersmile86911-Nov-12 6:34 
Questionhelp me Pin
bijarcity at 24-Oct-12 6:24
memberbijarcity24-Oct-12 6:24 
Questionvery helpful and tested with some scanners Pin
Member 6676 at 21-Oct-12 10:09
memberMember 667621-Oct-12 10:09 
QuestionNeed support, Pin
mastermindinfo at 25-Sep-12 5:25
membermastermindinfo25-Sep-12 5:25 
AnswerNeed support, till pending Pin
mastermindinfo at 3-Oct-12 0:47
membermastermindinfo3-Oct-12 0:47 
GeneralRe: Need support, till pending Pin
ingbabic at 25-Oct-12 5:56
memberingbabic25-Oct-12 5:56 
GeneralRe: Need support, till pending Pin
Abdullah Çetinkaya at 23-Jan-13 0:26
memberAbdullah Çetinkaya23-Jan-13 0:26 
GeneralMy vote of 4 Pin
Burak Tunçbilek at 7-Sep-12 5:09
memberBurak Tunçbilek7-Sep-12 5:09 
QuestionImage Resolution Problem. Pin
rush2rajiv at 29-Jun-12 1:06
memberrush2rajiv29-Jun-12 1:06 

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