Test on Different Platforms

Oct 13, 2025 by wbrum.org 139 views

Trouble Getting Started with Python 3 (Windows 11)

Hello, this looks like a very useful library, so I hope you can help me get started using it with Python 3.10, under Windows 11. I have run into a few problems. I am using the 64-bit version of the unicode DLL. The DTWDEMO64U program works correctly to access a local Epson scanner (over local network). This test program, modified from your python example, works well until I get to the dtwain_dll.DTWAIN_GetSourceProductNameW() call, which always fails with return value of -1 (DTWAIN_FAILURE1).

When I run the program, the source select window pops up and I can select my Epson printer, but when I query for the name of the TwainSource, I consistently get an empty string, with return code of -1. Note that I am using Python3, which is always Unicode as best I understand, and so I am using the "W" variants of the DLL entry points, as well using create_unicode_buffer() instead of create_string_buffer(). I tried all combinations of using the "A" or "W" or "" versions and with create_string_buffer() but that made no difference.

import dtwain
import ctypes as ct

def test_dtwain():
    
    # load the 64-bit unicode version of the dtwain dll
    dtwain_dll = ct.windll.LoadLibrary(".\\release_libraries\\dtwain64u.dll") 
    
    # is twain available?
    if not dtwain_dll.DTWAIN_IsTwainAvailable():
        print("Twain is not available")
        return
    else:
        print("Twain is available")  # prints Twain is available

    # Initialize DTWAIN
    rv = dtwain_dll.DTWAIN_SysInitialize()
    print(f"DTWAIN_SysInitialize returns: {rv}")  # returns 1
    
    # set up logging
    log_file = ct.create_unicode_buffer(".\\dtwain_log.log")
    rv = dtwain_dll.DTWAIN_SetTwainLogW(dtwain.DTWAIN_LOG_ALL, log_file) 
    print(f"DTWAIN_SetTwainLogW returns: {rv}") # returns 1
    
    # are we initialized?
    rv = dtwain_dll.DTWAIN_IsInitialized()
    print(f"DTWAIN_IsInitialized returns: {rv}")  # returns 1
    
    # Select a TWAIN source
    TwainSource = dtwain_dll.DTWAIN_SelectSource() # returns a non-zero handle to the selected source
    if TwainSource:
        # Display the product name of the Source
        mystrbuf = ct.create_unicode_buffer(30)
        rv = dtwain_dll.DTWAIN_GetSourceProductNameW(TwainSource, mystrbuf, len(mystrbuf)) # returns -1
        if rv == dtwain.DTWAIN_FAILURE1:
            print(f"rv = {rv} Failed to get source product name")
        else:
            print(f"Get source returns: {rv} with Source Product Name: {mystrbuf.value}")

        # Acquire to a BMP file
        rv = dtwain_dll.DTWAIN_AcquireFile(TwainSource, ".\\TEST.BMP", dtwain.DTWAIN_BMP, dtwain.DTWAIN_USELONGNAME,
                                      dtwain.DTWAIN_PT_DEFAULT, 1, 1, 1, 0) # returns 0
        # rv = dtwain_dll.DTWAIN_AcquireNative(TwainSource, dtwain.DTWAIN_PT_RGB , 1, 1, 1, 0)
        print(f"DTWAIN_AcquireFile returns: {rv}")  # returns 0

    # Close down DTWAIN                                      
    rv = dtwain_dll.DTWAIN_SysDestroy()

if __name__ == '__main__':
    test_dtwain()

The logfile is attached, if that might help. You can find it here: dtwain_log.log

Check the Log File: The log file is a good place to start. It may contain information about the error that is causing the DTWAIN_GetSourceProductNameW() call to fail.
Verify the DLL Version: Make sure that you are using the correct version of the DLL. In this case, you are using the 64-bit unicode version.
Check the Code: Review the code to make sure that it is correct. In this case, the code is using the "W" variants of the DLL entry points and create_unicode_buffer() instead of create_string_buffer().
Try a Different Approach: If the above steps do not work, try a different approach. For example, you could try using a different version of the DLL or a different programming language.

I hope this helps you get started with using the dtwain library with Python 3 on Windows 11. If you have any further questions or need additional help, please don't hesitate to ask.

Improve Error Handling: Improve error handling in the code to make it more robust.
Add More Features: Add more features to the code to make it more useful.
Test on Different Platforms: Test the code on different platforms to make sure it works correctly.

I would like to thank the dtwain library developers for creating such a useful library. I would also like to thank the Python 3 and Windows 11 documentation teams for creating such comprehensive documentation.
Trouble Getting Started with Python 3 (Windows 11) - Q&A

A: The dtwain library is a software development kit (SDK) that provides a set of APIs for working with TWAIN devices, such as scanners and cameras. You need it if you want to write a program that can communicate with TWAIN devices and perform tasks such as scanning and image acquisition.

A: TWAIN (Technology Without An Intrusive Interface) is a standard for communication between devices and applications. It allows devices to communicate with applications in a standardized way, making it easier to write programs that can work with multiple devices.

A: The benefits of using the dtwain library include:

Easy to use: The library provides a simple and intuitive API for working with TWAIN devices.
Cross-platform: The library can be used on multiple platforms, including Windows, macOS, and Linux.
High-performance: The library is optimized for high-performance, making it suitable for applications that require fast image acquisition and processing.

A: The system requirements for using the dtwain library are:

Windows 11: The library is compatible with Windows 11.
Python 3: The library requires Python 3 to be installed.
64-bit architecture: The library requires a 64-bit architecture to be installed.

A: To install the dtwain library, follow these steps:

Download the library: Download the dtwain library from the official website.
Install the library: Install the library using pip, the Python package manager.
Import the library: Import the library in your Python program using the import dtwain statement.

A: Some common issues that you may encounter when using the dtwain library include:

Error handling: The library may not handle errors well, leading to crashes or unexpected behavior.
Device compatibility: The library may not be compatible with all TWAIN devices, leading to errors or unexpected behavior.
Performance issues: The library may not perform well on certain systems or with certain devices, leading to slow image acquisition and processing.

A: To troubleshoot issues with the dtwain library, follow these steps:

Check the documentation: Check the official documentation for the library to see if there are any known issues or workarounds.
Check the error messages: Check the error messages to see if they provide any clues about the issue.
Contact the support team: Contact the support team for the library to see if they can provide any assistance.

A: The future plans for the dtwain library include:

Improving error handling: Improving error handling to make the library more robust.
Adding new features: Adding new features to the library to make it more useful.
Supporting new platforms: Supporting new platforms, such as macOS and Linux.

I hope this Q&A article has provided you with a better understanding of the dtwain library and how to use it. If you have any further questions or need additional help, please don't hesitate to ask.