[Bug]: Export of any image fails on 0.33.0 and higher win64

[wtpfede]

NegPy version / build

0.33.0 onwards - it works fine in 0.32.1 and below

OS

I am running Windows 10 Version 22H2 (OS Build 19045.6466)
My graphics card is an Nvdia GTX1070 on v 560.94

Scanner

Canonscan FS4000 US, Nikon Coolscan 4000, Minolta Dimage Scan Dual III - all exhibit same behaviour

Light source

Narrowband LED

Correction mode

None

Input ICC profile (if any)

Default

What happened

When exporting any file, either by right click, by using the export tab, or batch exporting, I get an "export complete - 1 failed" message in versions above 0.36.0.

I am not sure if there's any log or trace I can export and share with you to help debug this issue. I have checked it across versions and documented the behaviour below - basically something seems to have broken on 0.33.0 for me.

• In v 0.35.0 it fails silently (no "failed" message is displayed)
• In v 0.34.0 it declares "export successful" even though no file is exported
• In v 0.33.0 fails silently

Export function works fine in 0.32.1 included and any version below

Source file

I can't upload here because it's too large - please find a onedrive link here:
https://1drv.ms/i/c/39269ac2b331fe61/IQBXnDr1gAzmRqFEJsFkJC2qAZZNxKQQOsyWl9sl31UBOh8?e=eWyQ0y

Screenshots

[seanharding]

Can you share your negpy.log? I think on Windows it should be in Documents\NegPy\negpy.log. That might have the error in it.

[seanharding]

I don't know much about Windows, but I just successfully exported that file in Windows 11 running in a VM, with NegPy 0.50.0, so it's not 100% broken across the board. The log may help narrow down where and why it's failing.

[marcinz606]

try without GPU acceleration

[wtpfede]

Thank you both - I am now testing on 0.49.0 as I believe it is the most recent version. Let me know if you want me to try a different one.

@marcinz606 on the GPU acceleration - on a fresh install and even with GPU acceleration disable (the lightning icon goes from red to white), I am still getting the same error.

@seanharding thank you - I was able to find logs, here's what I could see

[2026-08-16 10:08:39] INFO     negpy.negpy.kernel.system.parallel: CPU parallel kernels: enabled (override=None, platform=win32)
[2026-08-16 10:08:39] INFO     negpy.negpy.infrastructure.storage.local_asset_store: LocalAssetStore initialized at C:\Users\tofed\Documents\NegPy\cache
[2026-08-16 10:08:40] INFO     negpy.negpy.infrastructure.gpu.device: WebGPU Backend: NVIDIA GeForce GTX 1070 (DiscreteGPU) via Vulkan
[2026-08-16 10:08:40] INFO     negpy.negpy.services.rendering.image_processor: ImageProcessor: Acceleration backend ready
[2026-08-16 10:08:40] INFO     negpy.negpy.services.rendering.image_processor: ImageProcessor: Acceleration backend ready
[2026-08-16 10:08:40] INFO     negpy.negpy.services.rendering.image_processor: ImageProcessor: Acceleration backend ready
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.gpu_engine: GPUEngine: VRAM resources released
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.preview_manager: load-timing decode.postprocess 38ms (fast=False) C:/Users/tofed/Desktop/dimage scans/2504-fuji100/c2025-04-13-0002.tif
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.preview_manager: load-timing decode.resize 19ms
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.preview_manager: load-timing decode.total 86ms (demosaic+orient+resize)
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.preview_manager: load-timing load_splash_and_linear 139ms (decode 86ms + open)
[2026-08-16 10:08:46] INFO     negpy.negpy.desktop.workers.render: load-timing preview_worker_total 142ms (load->buffer) C:/Users/tofed/Desktop/dimage scans/2504-fuji100/c2025-04-13-0002.tif
[2026-08-16 10:08:46] INFO     negpy.negpy.desktop.controller: load-timing preview_e2e 264ms (load request -> decoded buffer) C:/Users/tofed/Desktop/dimage scans/2504-fuji100/c2025-04-13-0002.tif
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.gpu_engine: load-timing gpu_init 71ms (compiled 21 shaders/pipelines)
[2026-08-16 10:08:46] INFO     negpy.negpy.services.rendering.gpu_engine: load-timing analysis 230ms (bounds=False refs=True anchor=True textural=True)
[2026-08-16 10:08:46] INFO     negpy.negpy.desktop.controller: load-timing first_render 494ms (buffer -> painted) C:/Users/tofed/Desktop/dimage scans/2504-fuji100/c2025-04-13-0002.tif
[2026-08-16 10:08:58] ERROR    negpy.negpy.desktop.controller: Worker failure: [WinError 5] Access is denied: 'C:\\Users\\tofed\\Desktop\\tmpkkjc6rua.part' -> 'C:/Users/tofed/Desktop\\test.jpg.jpg'
[2026-08-16 10:08:58] ERROR    negpy.negpy.infrastructure.storage.local_asset_store: Failed to save thumbnail 9158a6ed781946e50e8253c7faf55fb3d9299e9f3b5ce02453101abb16b47971: [Errno 13] Permission denied: 'C:\\Users\\tofed\\Documents\\NegPy\\cache\\thumbnails\\9158a6ed781946e50e8253c7faf55fb3d9299e9f3b5ce02453101abb16b47971.jpg'

• At first thought, this is a permission error so I run negpy again as administrator - but I still got that permission denied error.
• I also thought maybe my antivirus (Avast) is doing something odd so I disabled that for a few minutes, but still got exactly the same error.

So finally I thought, it might be how the installer is packaged, so I pointed the export folder to where I had installed Negpy (C/program Files/Negpy) and sure enough the thumbnail saving failed (see log below), but image saving succeeded.

[2026-08-16 10:15:00] ERROR negpy.negpy.infrastructure.storage.local_asset_store: Failed to save thumbnail 9158a6ed781946e50e8253c7faf55fb3d9299e9f3b5ce02453101abb16b47971: [Errno 13] Permission denied: 'C:\\Users\\tofed\\Documents\\NegPy\\cache\\thumbnails\\9158a6ed781946e50e8253c7faf55fb3d9299e9f3b5ce02453101abb16b47971.jpg'

So narrowing down the bug, it seems to me NegPy subprocesses/workers do not have permission to write to folders/directories outside of where it's installed, regardless of whether NegPy.exe is run as admin or not.

Let me know if there's something I can do to further help on this? Thanks as well for the time you put into this project.

[MohammedAlkindi]

Those two errors come from different code paths, which rules out a lock or a rename race: the export fails at the os.replace in export.py:207-210, but the thumbnail fails at a plain Image.save in local_asset_store.py:90. One cause blocks both, hits Documents and Desktop but not Program Files, survives elevation, and is unaffected by Avast: Defender's Controlled Folder Access. It protects exactly those folders and allow-lists per executable, so a path or signature change at 0.33.0 would drop NegPy off the list.

@wtpfede this settles it:

Get-MpPreference | Select-Object EnableControlledFolderAccess
Get-WinEvent -LogName "Microsoft-Windows-Windows Defender/Operational" -MaxEvents 200 | Where-Object { $_.Id -in 1123,1124 }

1 means enabled. I have not reproduced it: CFA is off on my machine.