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#1 Posted : Wednesday, January 17, 2018 9:07:11 PM(UTC)


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The 64-bit TWAIN Free Image Scanner virtual TWAIN driver has known compatibility issues with .NET 4.5 and above as well as with the C API DLLs that are built against VS2017. If you are using this TWAIN driver as a source with our LEADTOOLS TWAIN SDK and are having any issues, you will need to upgrade the FreeImagex64.dll that is included with the driver to v3.18.0.

The latest version can be downloaded from The FreeImage Project's site here: http://freeimage.sourceforge.net/download.html

Edited by moderator Tuesday, January 29, 2019 9:31:20 AM(UTC)  | Reason: Not specified

Hadi Chami
Developer Support Manager
LEAD Technologies, Inc.

thanks 1 user thanked Hadi for this useful post.
Walter on 1/18/2018(UTC)

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#2 Posted : Wednesday, January 19, 2022 4:43:02 PM(UTC)

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Recently a user requested additional information on the steps involved in making this change.
The screenshots below show the kinds of exceptions you may see in the LEAD C# OCR Twain Scanning Demo,
and below that you will find the steps to resolve.




Please do the following

Download and install the "TWAIN sample Data Source and Application" from Sourceforge.
TWAIN samples
zip file name (twainapp.win3264.zip)

Extract and run the x64 .msi in the - twainapp.win3264 - folder:

Now download the FreeImage library from here.


In the downloaded file folder check to make sure the file version of FreeImage.dll is

Make a copy of the FreeImage.dll and place it here:
Rename the old file in this location from "FreeImagex64.dll" to "FreeImagex64_Old.dll".
Then rename the new file from "FreeImage.dll" to "FreeImagex64.dll.

Once all of this is in place, run the TWAIN_APP_CMD32.exe project located here:
C:\Program Files (x86)\TWAIN Working Group\TWAIN 2.3 App Sample
use the following commands
>> cdsm - to connect
>> lds - to get a list of available scanners
>> cds# - to open source


With this still running, open the LEAD OcrTwainScanningDemo located here:
Be sure to update the framework
>> properties >> Application tab >> Set "Target framework" to .NET Framework 4.8

Run the OcrTwainScanning Demo project
Once open select a source by:
>> Twain >> Select Source... >> choose the "TWAIN2 FreeImage Software Scanner" virtual scanner
update the output location to where you would like the output file to be placed.


Pressed [Scan...] at the bottom left of the form.
The secondary page of the profile is displayed and when [Scan...] is selected the pdf is created, placed in the specified location, and should automatically open in Adobe if it is a pdf.


At this point, you should have the saved image from the scan in your output location.

Chris Thompson
Developer Support Engineer
LEAD Technologies, Inc.

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