Preview + Unit-tests for color conversions

1 files changed, 108 insertions, 0 deletions

diff --git a/internal/colors/hsl.go b/internal/colors/hsl.go
index 7477042..2a31f81 100644
--- a/internal/colors/hsl.go
+++ b/internal/colors/hsl.go
@@ -1 +1,109 @@
 package colors
+
+import (
+	"fmt"
+	"math"
+)
+
+type HSL struct {
+	H int // 0-360
+	S int // 0-100
+	L int // 0-100
+}
+
+func (h HSL) String() string {
+	return fmt.Sprintf("hsl(%d, %d, %d)", h.H, h.S, h.L)
+}
+
+func (h HSL) ToPrecise() PreciseColor {
+	// Normalize H, S, L
+	hue := float64(h.H) / 360.0
+	sat := float64(h.S) / 100.0
+	light := float64(h.L) / 100.0
+
+	var r, g, b float64
+
+	if sat == 0 {
+		// Achromatic case
+		r, g, b = light, light, light
+	} else {
+		var q float64
+		if light < 0.5 {
+			q = light * (1 + sat)
+		} else {
+			q = light + sat - (light * sat)
+		}
+		p := 2*light - q
+		r = hueToRGB(p, q, hue+1.0/3.0)
+		g = hueToRGB(p, q, hue)
+		b = hueToRGB(p, q, hue-1.0/3.0)
+	}
+
+	return PreciseColor{R: r, G: g, B: b}
+}
+
+func hueToRGB(p, q, t float64) float64 {
+	if t < 0 {
+		t += 1
+	}
+	if t > 1 {
+		t -= 1
+	}
+	if t < 1.0/6.0 {
+		return p + (q-p)*6*t
+	}
+	if t < 1.0/2.0 {
+		return q
+	}
+	if t < 2.0/3.0 {
+		return p + (q-p)*(2.0/3.0-t)*6
+	}
+	return p
+}
+
+func (h HSL) FromPrecise(p PreciseColor) ColorSpace {
+	r := p.R
+	g := p.G
+	b := p.B
+
+	max := math.Max(math.Max(r, g), b)
+	min := math.Min(math.Min(r, g), b)
+	delta := max - min
+
+	light := (max + min) / 2
+	var sat, hue float64
+
+	if delta == 0 {
+		// Achromatic case
+		hue, sat = 0, 0
+	} else {
+		if light < 0.5 {
+			sat = delta / (max + min)
+		} else {
+			sat = delta / (2 - max - min)
+		}
+
+		switch max {
+		case r:
+			hue = (g-b)/delta + (6 * boolToFloat64(g < b))
+		case g:
+			hue = (b-r)/delta + 2
+		case b:
+			hue = (r-g)/delta + 4
+		}
+		hue /= 6
+	}
+
+	return HSL{
+		H: int(math.Round(hue * 360)),
+		S: int(math.Round(sat * 100)),
+		L: int(math.Round(light * 100)),
+	}
+}
+
+func boolToFloat64(b bool) float64 {
+	if b {
+		return 1
+	}
+	return 0
+}