`SaneDev.snap()` raises `SANE_STATUS_INVAL` on Epson `epsonscan2` backend at any depth — works with `scanimage`
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Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 50/100
Research direction
Start by reproducing the Epson failure with the minimal Python example, then inspect SaneDev_snap's sane_read() loop where the issue reports SANE_STATUS_INVAL. Compare its behavior with the successful scanimage run and verify that dev.snap() completes and returns the expected 8-bit image at the reported settings.
Written by the indexing model from the issue text.
Description
Environment
- python-sane: 2.9.2 (both the distro package and a fresh
pip install .from this repo) - Python 3.13.13, openSUSE Leap 16.0
- SANE backend:
epsonscan2:Perfection V39/GT-S650:esci2:usb:ES010D:317 - Scanner: EPSON Perfection V39 / GT-S650 (USB)
Summary
SaneDev.snap() fails with _sane.error: Invalid argument (SANE_STATUS_INVAL) on every scan through the Epson epsonscan2 backend. The failure is independent of scan mode and depth — reproduced at 1-bit lineart and 8-bit grayscale. The same device scans cleanly with scanimage at both depths, so hardware, USB permissions and the backend itself are all functional.
Minimal reproducer
import sane
sane.init()
dev = sane.open("epsonscan2:Perfection V39/GT-S650:esci2:usb:ES010D:317")
dev.mode = "Grayscale"
dev.resolution = 300
dev.start()
print(dev.get_parameters()) # ('gray', 1, (2280, 2280), 8, 2280)
img = dev.snap() # raises _sane.error: Invalid argument
start() and get_parameters() return GOOD; the INVAL is raised inside SaneDev_snap's sane_read() loop. Cross-check: scanimage --mode Grayscale --resolution 300 > test.pnm completes and yields a valid 8-bit PGM.
Please see this issue in scantpaper for more details.
- Dominant language
- C
- Stars
- 61
- Forks
- 22
- PR merge metrics
- No merged PRs in 30d
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