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Actually compute proper foreground color for labels (#16729)
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parent
20efc6b56c
commit
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2 changed files with 53 additions and 12 deletions
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@ -8,6 +8,7 @@ package models
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import (
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"fmt"
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"html/template"
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"math"
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"regexp"
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"strconv"
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"strings"
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@ -138,19 +139,44 @@ func (label *Label) BelongsToRepo() bool {
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return label.RepoID > 0
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}
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// SrgbToLinear converts a component of an sRGB color to its linear intensity
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// See: https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation_(sRGB_to_CIE_XYZ)
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func SrgbToLinear(color uint8) float64 {
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flt := float64(color) / 255
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if flt <= 0.04045 {
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return flt / 12.92
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}
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return math.Pow((flt+0.055)/1.055, 2.4)
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}
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// Luminance returns the luminance of an sRGB color
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func Luminance(color uint32) float64 {
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r := SrgbToLinear(uint8(0xFF & (color >> 16)))
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g := SrgbToLinear(uint8(0xFF & (color >> 8)))
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b := SrgbToLinear(uint8(0xFF & color))
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// luminance ratios for sRGB
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return 0.2126*r + 0.7152*g + 0.0722*b
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}
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// LuminanceThreshold is the luminance at which white and black appear to have the same contrast
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// i.e. x such that 1.05 / (x + 0.05) = (x + 0.05) / 0.05
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// i.e. math.Sqrt(1.05*0.05) - 0.05
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const LuminanceThreshold float64 = 0.179
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// ForegroundColor calculates the text color for labels based
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// on their background color.
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func (label *Label) ForegroundColor() template.CSS {
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if strings.HasPrefix(label.Color, "#") {
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if color, err := strconv.ParseUint(label.Color[1:], 16, 64); err == nil {
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r := float32(0xFF & (color >> 16))
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g := float32(0xFF & (color >> 8))
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b := float32(0xFF & color)
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luminance := (0.2126*r + 0.7152*g + 0.0722*b) / 255
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// NOTE: see web_src/js/components/ContextPopup.vue for similar implementation
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luminance := Luminance(uint32(color))
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if luminance < 0.66 {
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// prefer white or black based upon contrast
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if luminance < LuminanceThreshold {
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return template.CSS("#fff")
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}
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return template.CSS("#000")
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}
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}
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@ -24,6 +24,22 @@ import {SvgIcon} from '../svg.js';
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const {AppSubUrl} = window.config;
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// NOTE: see models/issue_label.go for similar implementation
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const srgbToLinear = (color) => {
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color /= 255;
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if (color <= 0.04045) {
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return color / 12.92;
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}
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return ((color + 0.055) / 1.055) ** 2.4;
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};
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const luminance = (colorString) => {
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const r = srgbToLinear(parseInt(colorString.substring(0, 2), 16));
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const g = srgbToLinear(parseInt(colorString.substring(2, 4), 16));
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const b = srgbToLinear(parseInt(colorString.substring(4, 6), 16));
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return 0.2126 * r + 0.7152 * g + 0.0722 * b;
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};
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const luminanceThreshold = 0.179;
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export default {
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name: 'ContextPopup',
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@ -74,14 +90,13 @@ export default {
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labels() {
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return this.issue.labels.map((label) => {
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const red = parseInt(label.color.substring(0, 2), 16);
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const green = parseInt(label.color.substring(2, 4), 16);
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const blue = parseInt(label.color.substring(4, 6), 16);
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let color = '#ffffff';
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if ((red * 0.299 + green * 0.587 + blue * 0.114) > 125) {
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color = '#000000';
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let textColor;
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if (luminance(label.color) < luminanceThreshold) {
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textColor = '#ffffff';
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} else {
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textColor = '#000000';
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}
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return {name: label.name, color: `#${label.color}`, textColor: color};
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return {name: label.name, color: `#${label.color}`, textColor};
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});
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}
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},
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