Bug 493421

Summary:	Adjusting brightness and contrast sliders should show results immediately in preview window without re-pressing Preview button
Product:	[Applications] Skanlite	Reporter:	Robin Munn <rmunn>
Component:	general	Assignee:	Kåre Särs <kare.sars>
Status:	RESOLVED UPSTREAM
Severity:	wishlist	CC:	rmunn
Priority:	NOR
Version:	23.08.5
Target Milestone:	---
Platform:	Mint (Ubuntu based)
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Robin Munn 2024-09-21 05:37:51 UTC

SUMMARY

Adjusting brightness and contrast should immediately show results in preview window, without needing to press the Preview button again.

STEPS TO REPRODUCE
1. Click Preview button, scanner runs
2. Adjust brightness and/or contrast sliders in Advanced Options tab
3. No change in image until you click Preview button again, running the scanner again

OBSERVED RESULT

When trying to "dial in" the best brightness and contrast settings for the document I'm scanning, I have to click the Preview button multiple times, resulting in delays each time as the scanner re-scans the document.

EXPECTED RESULT

Adjusting brightness and/or contrast sliders should immediately show the result of the adjustment in the preview window, without the scanner needing to re-scan the image again.

SOFTWARE/OS VERSIONS
Linux Mint 22, using Cinnamon 6.2.9. Running `kinfo` in a terminal window produced errors I wasn't able to debug quickly, so the following is taken from the Skanlite "About" page instead.

Linux/KDE Plasma: Not using Plasma
KDE Plasma Version: N/A
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Skanlite Version: 23.08.5

Comment 1 Kåre Särs 2024-09-23 05:55:36 UTC

Thanks for the report.

I agree that it would be nice to have the preview updated when you modify the brightness and contrast sliders. Unfortunately implementing that has some big hurdles:
1) Brightness and contrast are implemented in the backends/drivers and not all of of them implement those options.
2) Brightness and contrast are applied to the raw input and not the already adjusted output, so the end result would be quite far off from the calculated guess. I would not be surprised if some scanners even would adjust the brightness of the lamp.

So the problem is basically that any image manipulation that we apply, would not reflect the actual result that you get when then doing the real scan, so the user would have to do a new preview anyways.

Sorry for not being able to fix the issue,
BR,
  Kåre