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Code Issues Wiki Activity

Actually compute proper foreground color for labels (#16729)

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Clar Fon 2021-08-25 13:55:47 -04:00 committed by GitHub
parent 20efc6b56c
commit 29b971b6d5
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2 changed files with 53 additions and 12 deletions
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36
models/issue_label.go
View file

@ -8,6 +8,7 @@ package models
import (
"fmt"
"html/template"
"math"
"regexp"
"strconv"
"strings"
@ -138,19 +139,44 @@ func (label *Label) BelongsToRepo() bool {
return label.RepoID > 0
}
// SrgbToLinear converts a component of an sRGB color to its linear intensity
// See: https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation_(sRGB_to_CIE_XYZ)
func SrgbToLinear(color uint8) float64 {
flt := float64(color) / 255
if flt <= 0.04045 {
return flt / 12.92
}
return math.Pow((flt+0.055)/1.055, 2.4)
}
// Luminance returns the luminance of an sRGB color
func Luminance(color uint32) float64 {
r := SrgbToLinear(uint8(0xFF & (color >> 16)))
g := SrgbToLinear(uint8(0xFF & (color >> 8)))
b := SrgbToLinear(uint8(0xFF & color))
// luminance ratios for sRGB
return 0.2126*r + 0.7152*g + 0.0722*b
}
// LuminanceThreshold is the luminance at which white and black appear to have the same contrast
// i.e. x such that 1.05 / (x + 0.05) = (x + 0.05) / 0.05
// i.e. math.Sqrt(1.05*0.05) - 0.05
const LuminanceThreshold float64 = 0.179
// ForegroundColor calculates the text color for labels based
// on their background color.
func (label *Label) ForegroundColor() template.CSS {
if strings.HasPrefix(label.Color, "#") {
if color, err := strconv.ParseUint(label.Color[1:], 16, 64); err == nil {
r := float32(0xFF & (color >> 16))
g := float32(0xFF & (color >> 8))
b := float32(0xFF & color)
luminance := (0.2126*r + 0.7152*g + 0.0722*b) / 255
// NOTE: see web_src/js/components/ContextPopup.vue for similar implementation
luminance := Luminance(uint32(color))
if luminance < 0.66 {
// prefer white or black based upon contrast
if luminance < LuminanceThreshold {
return template.CSS("#fff")
}
return template.CSS("#000")
}
}

29
web_src/js/components/ContextPopup.vue
View file

@ -24,6 +24,22 @@ import {SvgIcon} from '../svg.js';
const {AppSubUrl} = window.config;
// NOTE: see models/issue_label.go for similar implementation
const srgbToLinear = (color) => {
color /= 255;
if (color <= 0.04045) {
return color / 12.92;
}
return ((color + 0.055) / 1.055) ** 2.4;
};
const luminance = (colorString) => {
const r = srgbToLinear(parseInt(colorString.substring(0, 2), 16));
const g = srgbToLinear(parseInt(colorString.substring(2, 4), 16));
const b = srgbToLinear(parseInt(colorString.substring(4, 6), 16));
return 0.2126 * r + 0.7152 * g + 0.0722 * b;
};
const luminanceThreshold = 0.179;
export default {
name: 'ContextPopup',
@ -74,14 +90,13 @@ export default {
labels() {
return this.issue.labels.map((label) => {
const red = parseInt(label.color.substring(0, 2), 16);
const green = parseInt(label.color.substring(2, 4), 16);
const blue = parseInt(label.color.substring(4, 6), 16);
let color = '#ffffff';
if ((red * 0.299 + green * 0.587 + blue * 0.114) > 125) {
color = '#000000';
let textColor;
if (luminance(label.color) < luminanceThreshold) {
textColor = '#ffffff';
} else {
textColor = '#000000';
}
return {name: label.name, color: `#${label.color}`, textColor: color};
return {name: label.name, color: `#${label.color}`, textColor};
});
}
},