Fixed "Flow Stripe" FX and added palette support

[DedeHai]

the effect has been broken ever since it was added in 0.14.
The original effect used a float, the ported effect does not. The division therefore always results in 0 or 1 and thus not displaying any color spectrum but the same color for all LEDs.
Multiplying before the division fixes the effect back to its original intended look.

Added palette support while I was at it.

Summary by CodeRabbit

• Bug Fixes

  • Improved color calculation in the "Flow Stripe" effect for smoother and more accurate visual transitions.

• Enhancements

  • Updated the "Flow Stripe" effect to use palette-based colors, allowing for richer and more customizable color schemes.

[coderabbitai]

Walkthrough

The "Flow Stripe" effect function in the FX.cpp file was updated to correct the calculation of a variable for color scaling and to change the method of setting pixel colors from a direct HSV value to a palette-based lookup. The effect's metadata string was also updated to reflect palette usage.

Changes

File(s)	Change Summary
wled00/FX.cpp	Fixed variable calculation in "Flow Stripe" effect, switched to palette-based color setting, and updated effect metadata string.

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Reviewing files that changed from the base of the PR and between 00d1fcc and ea231cb.

📒 Files selected for processing (1)

• wled00/FX.cpp (1 hunks)

🧰 Additional context used

🧬 Code Graph Analysis (1)

wled00/FX.cpp (2)

wled00/FX.h (24)

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wled00/wled_math.cpp (2)

• sin8_t (82-86)
• sin8_t (82-82)

⏰ Context from checks skipped due to timeout of 90000ms (19)

• GitHub Check: wled_build / Build Environments (esp32s3_4M_qspi)
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🔇 Additional comments (4)

wled00/FX.cpp (4)

4820-4820: LGTM - Appropriate attribution added.

The comment update correctly credits the contributor who fixed the issue.

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4828-4828: Excellent fix for the integer division precision issue.

This change correctly addresses the core problem described in the PR. The original code (abs((int)i - hl) / hl) * 127 performed integer division first, causing most values to become 0 when abs(i - hl) < hl. The fixed version ((abs((int)i - hl) * 127) / hl) multiplies first, preserving precision and restoring the intended color spectrum effect.

The mathematical correctness is sound - for typical LED strip lengths, overflow is not a concern since the maximum value would be around 50000 * 127 = 6,350,000, which fits comfortably in an int.

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4832-4832: Palette support integration looks correct.

The transition from direct HSV color CHSV(b + hue, 255, 255) to palette-based lookup SEGMENT.color_from_palette(b + hue, false, true, 3) properly adds the requested palette functionality while maintaining the same hue calculation logic.

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4837-4837: Metadata string correctly updated for palette support.

The addition of pal=11 and the ! flag appropriately indicates that this effect now supports palettes, matching the code changes made to the effect implementation.

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