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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
View file

@ -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)
}

50
utils/colors_test.go
View file

@ -8,8 +8,7 @@ import (
)
const (
WCAGAAA float64 = 0.14285714285714285
WCAGAA float64 = 0.25
WCAGAA float64 = 3
)
func TestIntToRgb(t *testing.T) {
@ -19,38 +18,20 @@ func TestIntToRgb(t *testing.T) {
assert.Equal(t, uint8(0x56), b, "blue")
}
func TestIsDarkColor(t *testing.T) {
isDark := utils.IsDarkColor(0, 0, 0)
assert.True(t, isDark)
isLight := utils.IsDarkColor(255, 255, 255)
assert.False(t, isLight)
isQuestionable := utils.IsDarkColor(0x88, 0x88, 0x88)
assert.False(t, isQuestionable)
isReallyQuestionable := utils.IsDarkColor(0x00, 0x88, 0x00)
assert.True(t, isReallyQuestionable)
}
func TestBrighten(t *testing.T) {
r, g, b := utils.Brighten(0, 0, 0, 0.1)
assert.Equal(t, uint8(0x19), r)
assert.Equal(t, uint8(0x19), g)
assert.Equal(t, uint8(0x19), b)
// assert.LessOrEqual(t, WCAGAA, utils.WCAGRatio(
// utils.Luminance(0, 0, 0),
// utils.Luminance(r, g, b),
// ))
r, g, b = utils.Brighten(0x88, 0x88, 0x88, -0.1)
assert.Equal(t, uint8(0x88-0x19-1), r)
assert.Equal(t, uint8(0x88-0x19-1), g)
assert.Equal(t, uint8(0x88-0x19-1), b)
// assert.LessOrEqual(t, WCAGAA, utils.WCAGRatio(
// utils.Luminance(0x88, 0x88, 0x88),
// utils.Luminance(r, g, b),
// ))
assert.GreaterOrEqual(t, utils.WCAGRatio(
utils.Luminance(0x88, 0x88, 0x88),
utils.Luminance(r, g, b),
), WCAGAA)
}
func TestRgbToString(t *testing.T) {
@ -59,12 +40,21 @@ func TestRgbToString(t *testing.T) {
func TestAltColor(t *testing.T) {
r, g, b := utils.AltColor(0xa2, 0xc2, 0x42)
assert.Equal(t, uint8(0x09), r, "red")
assert.Equal(t, uint8(0x29), g, "green")
assert.Equal(t, uint8(0x00), b, "blue")
assert.Equal(t, uint8(0xf2), r, "red")
assert.Equal(t, uint8(0xef), g, "green")
assert.Equal(t, uint8(0xef), b, "blue")
assert.GreaterOrEqual(t, utils.WCAGRatio(
utils.Luminance(0xa2, 0xc2, 0x42),
utils.Luminance(r, g, b),
), WCAGAA)
r, g, b = utils.AltColor(0xa2, 0x15, 0x18)
assert.Equal(t, uint8(0xff), r, "red")
assert.Equal(t, uint8(0xed), g, "green")
assert.Equal(t, uint8(0xf0), b, "blue")
assert.Equal(t, uint8(0xff), r, "red2")
assert.Equal(t, uint8(0xed), g, "green2")
assert.Equal(t, uint8(0xf0), b, "blue2")
assert.GreaterOrEqual(t, utils.WCAGRatio(
utils.Luminance(0xa2, 0x15, 0x18),
utils.Luminance(r, g, b),
), WCAGAA)
}