DTWAIN Frequently Asked Questions
What is the DynaRithmic TWAIN Library (DTWAIN)?
Can you give me a list of the TWAIN devices that has
been tested with DTWAIN?
Before giving a list, please remember that DTWAIN is designed to work with any TWAIN compliant scanner, digital camera, webcam, or other TWAIN device. Since there are literally hundreds of different TWAIN devices, we cannot personally test each one. However, if the device follows the TWAIN specification, DTWAIN will control the device using the TWAIN protocol.
If this were not the case (DTWAIN cannot control the TWAIN device), then no third-party application could control the device correctly through the TWAIN protocol, since DTWAIN relies on using the TWAIN protocol to control the device. Therefore it is in the best interest of the manufacturer to make sure that libraries such as DTWAIN work correctly with their devices.
The list of TWAIN devices we have personally tested include the following (this is not an exhaustive list):
Fujitsu scanners (simplex and duplex models)
Canon LIDE and CanoScan series of scanners
CFM Twain drivers for SCSI-based scanners
We also have hundreds of other customers running flawlessly with TWAIN devices that we personally have not tested ourselves. Therefore you can be assured that if your device is TWAIN compliant, DTWAIN will work with it.
Will DTWAIN allow me to write my own TWAIN driver?
1) Adirectory that is listed in your system PATH environment variable, or
For a more detailed discussion,
MSDN link describes how Windows searches for DLL files.
I have a scanner that only has an
ISIS driver. Will DTWAIN work with it?
ISIS (Image and Scanner Interface Specification) is another scanner API developed by Pixel Translations (now EMC Captiva), much different than TWAIN. Since ISIS is a totally different scanner API, it is not supported by the DTWAIN library.
I would like to use DTWAIN, but my programming language is one not listed as a supported language. Can I still use DTWAIN?
If you are using a programming language that allows you to make calls to functions within DLL's, then your programming language can use DTWAIN. DTWAIN's functions follow the "stdcall" convention that most programming languages require, and the parameters that are passed to DTWAIN functions are generic to the Windows operating system (32-bit LONG integers, null-terminated strings, etc.).
Basically, DTWAIN has made sure that the DLL functions can be called by any programming language by providing the most generic, Windows API-like interface. No special VBString types, or C++ std::strings or anything like that are used a parameters to the DTWAIN functions, thereby making sure that your programming language can use the DTWAIN DLL.
Given this, practically every programming language that is used to develop Windows programs will allow you to make calls to DLL functions. The question really is "Using my programming language, how do I declare a function that resides in a DLL?". This question is difficult to answer, specifically for the reason that each language has their own way of defining functions that reside in DLL's.
Usually, the information to do this is found in your programming language user's manual, or maybe websites dedicated to the programming language that you're using. Searching for "calling DLL functions" will yield the correct information for your programming language. We have created the correct interfaces for Visual Basic (both 6.0 and .NET), C#, Delphi, FoxPro, and C/C++ (using the traditional header files that C and C++ uses).
I'm using Visual Basic 6.0. Do I need to run regsrvr.exe on the DTWAIN32.DLL to use it in Visual Basic?
No. DTWAIN32.DLL is not an ActiveX DLL. It is an ordinary Windows Dynamic Link Library, similar to the DLL's that reside in your Windows\system32 directory or similar directory. Given DTWAIN32.DLL is a regular DLL, Visual Basic programs must define the exported functions to use the DLL properly. These definitions are found in the DTWAIN32.BAS file, in which you add DTWAIN32.BAS to your VB projects.
Are .NET or ActiveX component
versions of DTWAIN available?
What licenses do I need if I want to distribute my
If you do not plan to distribute your DTWAIN applications, and are only using DTWAIN for personal use, you just need to purchase a Developer License for each developer working on your application.
If you plan to distribute your application on a company-wide basis, you will need to purchase a Company Distribution License in addition to Developer's License(s).
If you plan to distribute your application to the general public, i.e. shareware, commercial, or freeware, you must purchase a General Distribution Licensein addition to Developer's License(s).
If you plan to use DTWAIN in another programmer toolkit library, where your customers will need to make calls directly or indirectly to the DTWAIN functions themselves, you will need to email@example.com and discuss purchasing a Toolkit Distribution License.
For more information, please see theLicensing FAQ.
If I purchase a distribution license, do I need to pay extra royalties for distributing my applications?
I've upgraded to a newer version of the DTWAIN32.DLL to
fix a known issue with an older version of DTWAIN32.DLL,
however my program still doesn't work correctly.
What do I do now?
If you have verified that you're running the latest version, but the problem persists, please follow the directions here.
How do I determine what version of DTWAIN I have
1) To determine the version of
DTWAIN that will be used when running a program, use the
getversion.exe program found in the BIN subdirectory of
the DTWAIN installation. This program will
determine the version of DTWAIN that will be used when
you run your program.
Ideally, you would want to copy the getversion.exe program to where you will run your program, to see what version getversion.exe will detect. If you have multiple versions of DTWAIN installed on your system, getversion.exe will give the information of the version that will be used by your running program.
2) Call DTWAIN_GetVersionEx from your program. This function will return to your program the major version, minor version, whether DTWAIN is licensed or not, and the patch level.
3) You can use a DLL tool such as Dependency Walker or DumpBin to get the version number. DTWAIN versions are numbered as this:
So for example, version 22.214.171.124 means that the version is 2.3 with patch level 03.
I want to write a program
that does (a lot of things with the scanner), but I have
no experience with using DTWAIN. What's the
easiest thing to do to start writing DTWAIN programs?
Please look at the sample programs that are installed in the Examples subdirectory. The simplest program would be to check if TWAIN is installed, initialize DTWAIN, select a device, acquire an image to a file, and shutdown DTWAIN. Basically, this series of function calls
Please refer to the DTWAIN help file for further information on return values and parameters for these functions. Once these functions operate correctly, then you can start to experiment with the other aspects of setting your scanner's capabilities, and other more advanced features.
I have a scanner, and
DTWAIN doesn't seem to work with it. What can be
1) Make sure that DTWAIN will operate your scanner to some extent correctly by running the TestBed applications in the TestBed subdirectory of your DTWAIN installation. The DTWDEMO.EXE program is the most extensive of these applications.
2) As to your own program, check the return values from the DTWAIN functions. If there is an error that DTWAIN has detected, the function will return FALSE, NULL or some other value denoting that the function has failed. If a failure has occurred, the DTWAIN_GetLastError will return the exact error that caused the issue. Note that all DTWAIN functions that return an error do so for a reason, and that can be discovered by calling DTWAIN_GetLastError.
3) If there is no error that DTWAIN has detected, and the TestBed applications seem to work with your scanner, but there still is a problem, generate a TWAIN log (see DTWAIN_SetTwainLog). The TWAIN log will collect all calls made to DTWAIN, and calls made to the TWAIN system by DTWAIN. You can either examine the log file yourself (which isn't difficult once you get the hang of it), or you can submit it as a problem report firstname.lastname@example.org.
My scanner is TWAIN
compliant, I am scanning without the scanner's
user interface shown. My DTWAIN program seems to
not work correctly when the user interface is not shown,
but the program works correctly if I show the user
interface to the scanner. What is the issue here?
Acquiring without showing the scanner's user interface requires your program to make sure that all of the settings required by the TWAIN driver are set with your DTWAIN program. Remember that the user will not be making selections using the user interface, so your program has to set everything the TWAIN driver needs appropriately by calling DTWAIN functions to set the capabilities, pixel type, color type, number of pages, etc. before the scanning occurs.
Having stated this, there are a few
TWAIN drivers that do not operate correctly when the
user interface is not shown due to bugs in the TWAIN
driver. The probable reason for bugs
appearing is that the driver was meant to be used with
the user-interface being shown, and more than likely was
originally designed to work only in this mode. The
mode where the user interface is not shown was probably
not tested as thoroughly by the manufacturer.
The best you can do is identify these TWAIN Sources, and report these limitations to us at email@example.com.
I want to write a program
that does not show the scanner's user interface.
However, the user interface is always shown when my
program acquires images from the scanner, even if I
request that it not be shown. What is the problem?
Many TWAIN drivers do not allow operation without a user interface. Most of these TWAIN drivers are usually for digital cameras. Requesting to acquire images without a user interface is just that -- a request. A TWAIN driver does not have to honor the request of turning off the user interface, and will instead show the user interface.
The DTWAIN function DTWAIN_IsUIControllable will return TRUE if the user interface can be switched off. Your application should call this function before assuming that the user interface can be turned off.
I am communicating
with a TWAIN compliant digital camera, and I'm trying to
get the camera to take a picture using DTWAIN.
However, I can't seem to get this to work -- all that is
done is that DTWAIN downloads the images already stored
in the camera. Is there a way DTWAIN can make my
camera take pictures?
For most, if not all digital cameras, "acquiring" an image means to take the images already stored in the camera, and return a JPEG, Windows BMP, or similar image to the application. However, there are provisions within the TWAIN specification for a digital camera to take a picture. The issues with this is that very few digital cameras follow the TWAIN specification in terms of taking automatic pictures. Instead, many digital camera manufacturers have produced their own software development kits (SDK), independent of TWAIN. Examples are Kodak and Canon digital cameras.
You should first investigate whether there is an SDK available for your camera. If so, it is suggested you use the SDK that was developed specifically for the camera you're using. If your camera is one of the few that does support taking pictures using TWAIN, then there are functions to automatically capture an image. But please note -- your camera's TWAIN driver must have the capabilities to do this, otherwise using DTWAIN will not work for you (and neither will any other TWAIN package or software).
The bundled software that comes with my scanner allows
the scanner to (do some advanced functionality), but
DTWAIN cannot seem to duplicate what the bundled
software can do. What can be the problem?