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.NET TWAIN image scanner

, 12 May 2002 Public Domain 3M 82.9K 401
Using TWAIN API to scan images
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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

 
QuestionException throws when I use in Win7 64 bit Pin
anisfathima18-Apr-13 23:11
memberanisfathima18-Apr-13 23:11 
AnswerRe: Exception throws when I use in Win7 64 bit Pin
Jnnxp5-Aug-13 17:11
memberJnnxp5-Aug-13 17:11 
Questionhow set Image info Pin
Mohamed Nabawy15-Apr-13 7:59
memberMohamed Nabawy15-Apr-13 7:59 
QuestionScanner Error Pin
asheykh14-Apr-13 23:05
memberasheykh14-Apr-13 23:05 
QuestionTwainCommand.TransferReady: hbitmap to gdi+ bitmap Pin
liuxu093826-Mar-13 22:21
memberliuxu093826-Mar-13 22:21 
QuestionThe "twaingui_demo.zip" is damaged? Pin
liuxu093826-Mar-13 1:16
memberliuxu093826-Mar-13 1:16 
QuestionScanning on Win7 64Bit Pin
khalilsa27-Feb-13 5:19
memberkhalilsa27-Feb-13 5:19 
AnswerRe: Scanning on Win7 64Bit Pin
ricardofrias20-Mar-13 8:48
memberricardofrias20-Mar-13 8:48 
AnswerRe: Scanning on Win7 64Bit Pin
Jnnxp5-Aug-13 17:12
memberJnnxp5-Aug-13 17:12 
Questionuse in asp.net? Pin
Kalpana Volety11-Jan-13 10:59
memberKalpana Volety11-Jan-13 10:59 
AnswerRe: use in asp.net? Pin
Jnnxp5-Aug-13 17:17
memberJnnxp5-Aug-13 17:17 
QuestionWIA driver is not working with multiple pages Pin
anisfathima9-Jan-13 23:59
memberanisfathima9-Jan-13 23:59 
AnswerRe: WIA driver is not working with multiple pages Pin
smile869114-Feb-13 9:51
membersmile869114-Feb-13 9:51 
Bughow set boolean value CAP_PAPERDETECTABLE,ICAP_AUTOMATICDESKEW ecc..? Pin
nturri13065-Jan-13 6:07
membernturri13065-Jan-13 6:07 
i tried in various mode to set , but I always get an error

i see in the source needless to set the types bool, because?

could this be the problem must be set differently and how ?

thanks
QuestionNeed help Pin
Member 806548423-Nov-12 18:54
memberMember 806548423-Nov-12 18:54 
AnswerRe: Need help Pin
Abdullah Çetinkaya23-Jan-13 0:11
memberAbdullah Çetinkaya23-Jan-13 0:11 
Questionget error in multipage scanning Pin
yuee17-Nov-12 3:08
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AnswerRe: get error in multipage scanning Pin
smile86917-Nov-12 3:09
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Questionhelp Pin
bijarcity24-Oct-12 7:09
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AnswerRe: help Pin
smile86911-Nov-12 6:34
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Questionhelp me Pin
bijarcity24-Oct-12 6:24
memberbijarcity24-Oct-12 6:24 
Questionvery helpful and tested with some scanners Pin
Member 667621-Oct-12 10:09
memberMember 667621-Oct-12 10:09 
QuestionNeed support, Pin
mastermindinfo25-Sep-12 5:25
membermastermindinfo25-Sep-12 5:25 
AnswerNeed support, till pending Pin
mastermindinfo3-Oct-12 0:47
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GeneralRe: Need support, till pending Pin
ingbabic25-Oct-12 5:56
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GeneralRe: Need support, till pending Pin
Abdullah Çetinkaya23-Jan-13 0:26
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GeneralMy vote of 4 Pin
Burak Tunçbilek7-Sep-12 5:09
memberBurak Tunçbilek7-Sep-12 5:09 
QuestionImage Resolution Problem. Pin
rush2rajiv29-Jun-12 1:06
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AnswerRe: Image Resolution Problem. Pin
Member 1018928526-Aug-13 18:53
memberMember 1018928526-Aug-13 18:53 
QuestionOut of Memory Exception Pin
Jaydeep Jadav15-Jun-12 21:56
memberJaydeep Jadav15-Jun-12 21:56 
QuestionRe: Out of Memory Exception Pin
nileshkakade26-Feb-13 20:17
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AnswerRe: Out of Memory Exception Pin
Jaydeep Jadav2-Mar-13 0:18
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QuestionLoader Lock Error Problem Pin
leenak8-Jun-12 3:11
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GeneralRe: Loader Lock Error Problem [modified] Pin
smile869110-Jul-12 12:59
membersmile869110-Jul-12 12:59 
QuestionDuplex Scanning Pin
Isuru Alahakoon8-Jun-12 2:14
memberIsuru Alahakoon8-Jun-12 2:14 
Questionhide progress bar window. Pin
Member 46759534-Jun-12 22:32
memberMember 46759534-Jun-12 22:32 
QuestionError on 64 bits machine Pin
david bong1-Jun-12 7:09
memberdavid bong1-Jun-12 7:09 
AnswerRe: Error on 64 bits machine Pin
boblogan13-Jun-12 7:00
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GeneralRe: Error on 64 bits machine Pin
Abdullah Çetinkaya23-Jan-13 0:33
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Questionset Flatbed or Feader Pin
Andrew8231-May-12 22:22
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QuestionCan use project as web Pin
ramysamir29-May-12 1:40
memberramysamir29-May-12 1:40 
QuestionDo you have code for automatically control scanner Pin
golanw12-May-12 23:52
membergolanw12-May-12 23:52 
QuestionDLL Pin
Member 888329025-Apr-12 10:57
memberMember 888329025-Apr-12 10:57 
QuestionHow Can I change scaning variables with c# code? Pin
Radu23717-Apr-12 21:46
memberRadu23717-Apr-12 21:46 
AnswerRe: How Can I change scaning variables with c# code? Pin
Member 100259915-May-13 17:36
memberMember 100259915-May-13 17:36 
QuestionHow to check scanner is connected befor Acquire Pin
swapnil7434513-Apr-12 22:02
memberswapnil7434513-Apr-12 22:02 
Questionconverting? Pin
darkalastair19-Mar-12 23:15
memberdarkalastair19-Mar-12 23:15 
AnswerRe: converting? Pin
Member 667621-Oct-12 9:58
memberMember 667621-Oct-12 9:58 
QuestionTwainLib Visual Studio 2010 Windows 7 64 bit Pin
sanvi615-Mar-12 4:10
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AnswerRe: TwainLib Visual Studio 2010 Windows 7 64 bit Pin
UstesGreenridge26-Mar-12 4:55
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