Unable to scan documents: "unsupported pixel type"

[Frank]

Hi people,

Worked great for me NAPS, but not any more unfortunately.
I get an error "unsupported pixel type" when scanning 256bit color documents.
I don't get this error when scanning greyscale or full RGB documents.

When scanning knob is pressed, the Twain driver activates my scanner, opens the twain dialogue box and starts scanning. When this windows is closed, NAPS2 pops up with a error as indicated.

NAPS version 7.3.0.0, Windows 10 pro, 64bit.
System.ArgumentException: Unsupported pixel type: 8 3 1 8,0,0,0,0,0,0,0
at void NAPS2.Scan.Internal.Twain.TwainMemoryBufferReader.CopyBufferToImage(TwainMemoryBuffer memoryBuffer, TwainImageData imageData, IMemoryImage outputImage)
at void NAPS2.Scan.Internal.Twain.TwainImageProcessor.MemoryBufferTransferred(TwainMemoryBuffer memoryBuffer)
at async Task NAPS2.Remoting.Worker.WorkerServiceAdapter.TwainScan(ScanOptions options, CancellationToken cancelToken, ITwainEvents twainEvents)
at async Task NAPS2.Scan.Internal.Twain.RemoteTwainSessionController.StartScan(ScanOptions options, ITwainEvents twainEvents, CancellationToken cancelToken)
at async Task NAPS2.Scan.Internal.Twain.TwainScanDriver.Scan(ScanOptions options, CancellationToken cancelToken, IScanEvents scanEvents, Action<imemoryimage> callback)+(?) => { }
at async Task NAPS2.Scan.Internal.RemoteScanController.Scan(ScanOptions options, CancellationToken cancelToken, IScanEvents scanEvents, Action<processedimage, postprocessingcontext=""> callback)
at async IAsyncEnumerable<processedimage> NAPS2.Scan.ScanController.Scan(ScanOptions options, CancellationToken cancelToken)+(?) => { }</processedimage></processedimage,></imemoryimage>

Any clue how this problem can be solved?

Thanks in advance,

[Ben Olden-Cooligan]

In your profile settings, under Advamced, Twain Implementation, you can try selecting Native Transfer. NAPS2 doesn't currently support palette-based colors by default.

[Frank]

Dear Ben,
you''re fast in answering questions :)

I select Native Transfer in my settings, see attachment.

I use this, so I can use full options of my scanner, including things like pre-defined settings I also use in other programs and document feeder and of course the possibility to scan 256bit colour - that saves a lot of disk space compared to full colour.

256bit is not a palette AFAIK (one of the standards)? It is just 8 bits per pixel and saves me a lot of disk space.

[Ben Olden-Cooligan]

I think it was lost in translation, here's what you need to set.

[Frank]

Dear Ben,

Just tried your option and seems to do the job :)

Thanks for your support,

Frank