role color stuff

utils/colors.go

@@ -1,13 +1,18 @@
 package utils
 
-import "math"
+import (
+	"fmt"
+	"math"
+)
+
+const (
+	Pred   float64 = 0.299
+	Pgreen float64 = 0.587
+	Pblue  float64 = 0.114
+)
 
 func IsDarkColor(r, g, b uint8) bool {
-	rC := 0.299 * math.Pow(float64(r), 2)
-	gC := 0.587 * math.Pow(float64(g), 2)
-	bC := 0.114 * math.Pow(float64(b), 2)
-
-	lum := math.Sqrt(rC + gC + bC)
+	lum := Luminance(r, g, b)
 
 	return lum <= 130
 }
@@ -19,3 +24,47 @@ func IntToRgb(color uint32) (uint8, uint8, uint8) {
 
 	return uint8(r), uint8(g), uint8(b)
 }
+
+func RgbToString(r, g, b uint8) string {
+	return fmt.Sprintf("#%02x%02x%02x", r, g, b)
+}
+
+func AltColor(r, g, b uint8) (uint8, uint8, uint8) {
+	brightnessAmount := -0.6
+	if IsDarkColor(r, g, b) {
+		brightnessAmount = 0.85
+	}
+	return Brighten(r, g, b, brightnessAmount)
+}
+
+func Brighten(r, g, b uint8, amount float64) (uint8, uint8, uint8) {
+	return multiply(r, amount), multiply(g, amount), multiply(b, amount)
+}
+
+func multiply(i uint8, amount float64) uint8 {
+	iF := float64(i)
+	return uint8(
+		math.Max(
+			0,
+			math.Min(
+				255, iF+255*amount,
+			),
+		),
+	)
+}
+
+func Luminance(r, g, b uint8) float64 {
+	rC := Pred * math.Pow(float64(r), 2)
+	gC := Pgreen * math.Pow(float64(g), 2)
+	bC := Pblue * math.Pow(float64(b), 2)
+
+	return math.Sqrt(rC + gC + bC)
+}
+
+func WCAGRatio(l1, l2 float64) float64 {
+	if l1 < l2 {
+		return (l1 + 0.05) / (l2 + 0.05)
+	} else {
+		return (l2 + 0.05) / (l1 + 0.05)
+	}
+}