Click here to Skip to main content
12,402,189 members (66,289 online)
Click here to Skip to main content
Add your own
alternative version

Stats

3.4M views
96.3K downloads
408 bookmarked
Posted

.NET TWAIN image scanner

, 12 May 2002 Public Domain
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

 
AnswerRe: Connect to network scanner Pin
James West1-Nov-09 12:08
memberJames West1-Nov-09 12:08 
AnswerEpson Supported Twain Commands Pin
JohnSims19421-Sep-09 1:07
memberJohnSims19421-Sep-09 1:07 
AnswerScanner with Document Feeder Pin
JohnSims19421-Sep-09 1:05
memberJohnSims19421-Sep-09 1:05 
GeneralRe: Scanner with Document Feeder Pin
Member 39132834-Nov-09 23:23
memberMember 39132834-Nov-09 23:23 
GeneralRe: Scanner with Document Feeder Pin
Member 39132834-Nov-09 23:35
memberMember 39132834-Nov-09 23:35 
AnswerRe: Scanner with Document Feeder Pin
JohnSims1944-Nov-09 23:50
memberJohnSims1944-Nov-09 23:50 
GeneralRe: Scanner with Document Feeder Pin
zlov29-Sep-10 0:17
memberzlov29-Sep-10 0:17 
QuestionPassing a string to TwCapability Pin
JohnSims19421-Sep-09 0:46
memberJohnSims19421-Sep-09 0:46 
GeneralDSuserif will cause exception AccessViolationException: Pin
carlshe19-Sep-09 20:17
membercarlshe19-Sep-09 20:17 
GeneralRe: DSuserif will cause exception AccessViolationException: Pin
LupinTheThird30-Oct-11 10:50
memberLupinTheThird30-Oct-11 10:50 
QuestionHow to implement it to the User Control Pin
chandresh.softobiz16-Sep-09 17:50
memberchandresh.softobiz16-Sep-09 17:50 
GeneralIs it possible to scan just one document from feeder Pin
zodiacseven11-Aug-09 3:20
memberzodiacseven11-Aug-09 3:20 
GeneralUse Duplex with Driver Twain - Help URGENT Pin
IvesBertoli30-Jul-09 2:44
memberIvesBertoli30-Jul-09 2:44 
GeneralRe: Use Duplex with Driver Twain - Help URGENT Pin
JohnSims19418-Sep-09 0:47
memberJohnSims19418-Sep-09 0:47 
GeneralRe: Use Duplex with Driver Twain - Help URGENT Pin
bennyshani19-Oct-09 11:38
memberbennyshani19-Oct-09 11:38 
GeneralRe: Use Duplex with Driver Twain -Going Insane Pin
morke4-Jan-10 1:23
membermorke4-Jan-10 1:23 
GeneralRe: Use Duplex with Driver Twain -Going Insane Pin
bennyshani4-Jan-10 3:19
memberbennyshani4-Jan-10 3:19 
GeneralRe: Use Duplex with Driver Twain -Going Insane Pin
morke4-Jan-10 23:02
membermorke4-Jan-10 23:02 
Generalrunning to dead when cancel Pin
pclion17-Jun-09 18:04
memberpclion17-Jun-09 18:04 
AnswerRe: running to dead when cancel Pin
Wolexie21-Jun-09 2:01
memberWolexie21-Jun-09 2:01 
Generalchange the source of the image to be acquire Pin
PRProgrmmerAlexG9-Jun-09 11:09
memberPRProgrmmerAlexG9-Jun-09 11:09 
GeneralRe: change the source of the image to be acquire Pin
Vankir24-Nov-09 7:07
memberVankir24-Nov-09 7:07 
General1bpp b/w DIB problem Pin
nasharu17-Apr-09 8:27
membernasharu17-Apr-09 8:27 
GeneralRe: 1bpp b/w DIB problem Pin
__Gianluca__13-Oct-09 3:10
member__Gianluca__13-Oct-09 3:10 
GeneralYou are a living legend! Pin
martincook6-Apr-09 8:31
membermartincook6-Apr-09 8:31 
QuestionUsing Twain driver : dsuerif does not wait user response from userinterface and returns directly a SUCCESS call Pin
Member 39059881-Apr-09 0:42
memberMember 39059881-Apr-09 0:42 
Question[Ask] 2 Image in one Click Pin
Reivina15-Mar-09 22:49
memberReivina15-Mar-09 22:49 
AnswerRe: [Ask] 2 Image in one Click Pin
ppmax17-Mar-09 3:57
memberppmax17-Mar-09 3:57 
JokeRe: [Ask] 2 Image in one Click Pin
Wolexie10-Jun-09 1:44
memberWolexie10-Jun-09 1:44 
GeneralRe: [Ask] 2 Image in one Click Pin
realfake116-Sep-09 21:14
memberrealfake116-Sep-09 21:14 
GeneralRe: [Ask] 2 Image in one Click Pin
nakashi27-Nov-11 2:04
membernakashi27-Nov-11 2:04 
GeneralPb with Threading Pin
ppmax9-Mar-09 22:49
memberppmax9-Mar-09 22:49 
Generalscanner & application is gettig hanged Pin
amitnashtekar4-Mar-09 19:13
memberamitnashtekar4-Mar-09 19:13 
General[HELP]No "Select Source..." window appears! Pin
Palermo4ever16-Feb-09 4:32
memberPalermo4ever16-Feb-09 4:32 
GeneralRe: [HELP]No "Select Source..." window appears! Pin
Fiorebat17-Apr-09 2:12
memberFiorebat17-Apr-09 2:12 
QuestionPrinting Profile Pin
kengct5-Feb-09 18:45
memberkengct5-Feb-09 18:45 
GeneralTransferring ONE image a time [modified] Pin
arkiduck28-Jan-09 1:54
memberarkiduck28-Jan-09 1:54 
GeneralGdipSaveImageToFile function lock file [modified] Pin
lex-luthor27-Jan-09 6:34
memberlex-luthor27-Jan-09 6:34 
GeneralUnable to load DLL 'twain_32.dll': A dynamic link library (DLL) initialization routine failed. (Exception from HRESULT: 0x8007045A) Pin
Member 418037421-Jan-09 23:57
memberMember 418037421-Jan-09 23:57 
GeneralSupportedSizes doesnt work Pin
Member 37116407-Nov-08 3:37
memberMember 37116407-Nov-08 3:37 
GeneralRe: SupportedSizes doesnt work Pin
Member 37116407-Nov-08 3:44
memberMember 37116407-Nov-08 3:44 
GeneralRe: SupportedSizes doesnt work Pin
Ninos Denkha17-Mar-11 12:56
memberNinos Denkha17-Mar-11 12:56 
GeneralNo response after acquire(); Pin
kengct6-Nov-08 18:29
memberkengct6-Nov-08 18:29 
RantRe: No response after acquire(); Pin
kengct12-Nov-08 23:46
memberkengct12-Nov-08 23:46 
GeneralRe: No response after acquire(); Pin
hom_rcp25-Dec-08 4:45
memberhom_rcp25-Dec-08 4:45 
GeneralRe: No response after acquire(); Pin
kengct12-Jan-09 21:10
memberkengct12-Jan-09 21:10 
GeneralRe: No response after acquire(); Pin
Joey Burgett17-Mar-09 16:20
memberJoey Burgett17-Mar-09 16:20 
Questionhow to scan image directly into picturebox instead of painting onto form? Pin
Juraj Suchan16-Oct-08 11:13
memberJuraj Suchan16-Oct-08 11:13 
AnswerRe: how to scan image directly into picturebox instead of painting onto form? Pin
Gary Noter9-Dec-08 11:16
memberGary Noter9-Dec-08 11:16 
GeneralRe: how to scan image directly into picturebox instead of painting onto form? Pin
Burhan ERSOY28-Jul-09 22:52
memberBurhan ERSOY28-Jul-09 22:52 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    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 | 2.8.160721.1 | Last Updated 13 May 2002
Article Copyright 2001 by NETMaster
Everything else Copyright © CodeProject, 1999-2016
Layout: fixed | fluid