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catch mid colors outside of WCAG AA

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This commit is contained in:
41666 2025-04-06 17:28:26 -07:00
parent f72c7a357b
commit df33164b08
28 changed files with 135 additions and 96 deletions
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54
utils/colors.go
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@ -2,6 +2,7 @@ package utils
import (
"fmt"
"log"
"math"
)
@ -11,11 +12,10 @@ const (
Pblue float64 = 0.114
)
func IsDarkColor(r, g, b uint8) bool {
lum := Luminance(r, g, b)
return lum <= 130
}
var (
DarkAltFallback = []uint8{0x1c, 0x10, 0x10}
LightAltFallback = []uint8{0xf2, 0xef, 0xef}
)
func IntToRgb(color uint32) (uint8, uint8, uint8) {
b := color % 256
@ -30,11 +30,30 @@ func RgbToString(r, g, b uint8) string {
}
func AltColor(r, g, b uint8) (uint8, uint8, uint8) {
l1 := Luminance(r, g, b)
isDark := l1 <= 0.5098
brightnessAmount := -0.6
if IsDarkColor(r, g, b) {
if isDark { // color is dark
brightnessAmount = 0.85
}
return Brighten(r, g, b, brightnessAmount)
r2, g2, b2 := Brighten(r, g, b, brightnessAmount)
l2 := Luminance(r2, g2, b2)
ratio := WCAGRatio(l1, l2)
log.Printf("isDark=%v, ratio: %f, l1(%f)=%s, l2(%f)=%s", isDark, ratio, l1, RgbToString(r, g, b), l2, RgbToString(r2, g2, b2))
if ratio >= 3 {
return r2, g2, b2
}
if isDark {
return LightAltFallback[0], LightAltFallback[1], LightAltFallback[2]
} else {
return DarkAltFallback[0], DarkAltFallback[1], DarkAltFallback[3]
}
}
func Brighten(r, g, b uint8, amount float64) (uint8, uint8, uint8) {
@ -53,18 +72,23 @@ func multiply(i uint8, amount float64) uint8 {
)
}
func sRGB(c uint8) float64 {
cf := float64(c) / 255
if cf <= 0.03928 {
return cf / 12.92
} else {
return math.Pow((cf+0.055)/1.055, 2.4)
}
}
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)
rC := Pred * math.Pow(sRGB(r), 2)
gC := Pgreen * math.Pow(sRGB(g), 2)
bC := Pblue * math.Pow(sRGB(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)
}
return (math.Max(l1, l2) + 0.05) / (math.Min(l1, l2) + 0.05)
}