Remove gamma value lower limit to enable inverse gamma correction

[flo269]

Summary

Remove the artificial restriction that prevents gamma values below 1.0, enabling inverse gamma correction.

Motivation

LEDs can appear too dark at low brightness levels. Inverse gamma correction (gamma < 1.0) is needed to brighten the lower end of the brightness curve and make dimmed LEDs more visible.

Currently, gamma values are restricted to > 1.0, which only allows standard gamma correction. This PR removes that limitation.

Changes

• Update validation in set.cpp and cfg.cpp to allow gamma range 0.1-3.0 (was 1.0-3.0)
• Update HTML form validation in settings_leds.htm to match (min="0.1")

Technical Details

The NeoGammaWLEDMethod::calcGammaTable() function already supports any gamma value mathematically. This PR simply removes an artificial restriction that prevented values < 1.0.

Testing

Tested on v0.15.3 and latest main - inverse gamma values (< 1.0) now work correctly and improve visibility at low brightness levels.

Summary by CodeRabbit

• Bug Fixes
  • Expanded valid gamma correction range from [1.0–3.0] to [0.1–3.0]; values between 0.1 and 1.0 are now accepted rather than being reset.
  • Updated the gamma value input to allow a minimum of 0.1, matching the new validation and enabling finer calibration.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

Expand the acceptable range for gamma correction values by lowering the minimum threshold from 1.0 to 0.1 across validation logic and UI input constraints, allowing values in the range [0.1, 3] instead of [1.0, 3].

Changes

Cohort / File(s)	Summary
Gamma correction validation logic wled00/cfg.cpp, wled00/set.cpp	Lowered the lower-bound check for gammaCorrectVal from 1.0 to 0.1 (<= 1.0f → < 0.1f), accepting values in [0.1, 3]; out-of-range values still reset gamma and related flags and trigger gamma table recalculation/fallback.
UI input constraints wled00/data/settings_leds.htm	Changed the min attribute for the gamma input from 1 to 0.1 to match backend validation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add pre-applied gamma to c3g & (some) fastled palettes to match original look #4711: Adjusts default gammaCorrectVal (2.8→2.2) and palette pre-gamma; relates to gamma handling and defaults.
• add inverse gamma 32 function and fix colors in pride #4722: Modifies gamma validation/behavior in cfg.cpp and related gamma logic.

Suggested reviewers

• blazoncek

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately reflects the main change: removing the gamma value lower limit (from 1.0 to 0.1) to enable inverse gamma correction, which is the core objective and change across all modified files.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between eeb5144 and 9d55b18.

📒 Files selected for processing (3)

• wled00/cfg.cpp
• wled00/data/settings_leds.htm
• wled00/set.cpp

🚧 Files skipped from review as they are similar to previous changes (3)

• wled00/data/settings_leds.htm
• wled00/cfg.cpp
• wled00/set.cpp

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[DedeHai]

Did you check both gamma functions create correct tables for the new range?

[DedeHai]

I checked the functions, they do work still.
you also need to update the other lines in the config so it works after a reboot.

[DedeHai]

update this

[flo269]

I think I have it figured out - updated lines 511 and 513 to check != 1.0f instead of > 1.0f so gamma correction is enabled for any non-linear value (both below and above 1.0). This should fix the persistence issue after reboot.