qmk-rgb/internal/rgb/effects.go

package rgb

import (
	"fmt"
	"math"
	"strconv"
)

// LEDParam defines QMK rgblight parameter indices.
type LEDParam uint8

const (
	Brightness LEDParam = 1
	EffectID   LEDParam = 2
	Speed      LEDParam = 3
	ColorValue LEDParam = 4

	Mode   LEDParam = EffectID
	Enable LEDParam = EffectID
)

// Color represents an RGB color.
type Color struct {
	R uint8
	G uint8
	B uint8
}

// ParseHexColor parses a 6-digit hex color string (e.g. "ff0000").
func ParseHexColor(s string) (Color, error) {
	if len(s) != 6 {
		return Color{}, fmt.Errorf("invalid hex color: %s", s)
	}

	r, err := strconv.ParseUint(s[0:2], 16, 8)
	if err != nil {
		return Color{}, fmt.Errorf("invalid hex color: %s", s)
	}
	g, err := strconv.ParseUint(s[2:4], 16, 8)
	if err != nil {
		return Color{}, fmt.Errorf("invalid hex color: %s", s)
	}
	b, err := strconv.ParseUint(s[4:6], 16, 8)
	if err != nil {
		return Color{}, fmt.Errorf("invalid hex color: %s", s)
	}
	return Color{R: uint8(r), G: uint8(g), B: uint8(b)}, nil
}

// HSV converts the color to HSV (QMK rgblight uses 0-255 ranges for H, S, V).
func (c Color) HSV() (h, s, v uint8) {
	r, g, b := float64(c.R), float64(c.G), float64(c.B)
	max := math.Max(r, math.Max(g, b))
	min := math.Min(r, math.Min(g, b))
	v = uint8(max)

	d := max - min
	if d == 0 {
		return 0, 0, v
	}

	if max > 0 {
		s = uint8((d / max) * 255)
	} else {
		return 0, 0, 0
	}

	var hFloat float64
	switch {
	case max == r:
		hFloat = ((g - b) / d) * 60.0
	case max == g:
		hFloat = ((b-r)/d)*60.0 + 120.0
	case max == b:
		hFloat = ((r-g)/d)*60.0 + 240.0
	}

	if hFloat < 0 {
		hFloat += 360.0
	}

	h = uint8((hFloat / 360.0) * 255.0)
	if h >= 255 {
		h = 254
	}

	return h, s, v
}