Modify luminance calculation and extract related functions into single files

models/issues/label.go

@@ -159,33 +159,6 @@ func (l *Label) BelongsToRepo() bool {
  return l.RepoID > 0
 }
 
-// Get color as RGB values in 0..255 range
-func (l *Label) ColorRGB() (float64, float64, float64, error) {
- color, err := strconv.ParseUint(l.Color[1:], 16, 64)
- if err != nil {
- return 0, 0, 0, err
- }
-
- r := float64(uint8(0xFF & (uint32(color) >> 16)))
- g := float64(uint8(0xFF & (uint32(color) >> 8)))
- b := float64(uint8(0xFF & uint32(color)))
- return r, g, b, nil
-}
-
-// Determine if label text should be light or dark to be readable on background color
-func (l *Label) UseLightTextColor() bool {
- if strings.HasPrefix(l.Color, "#") {
- if r, g, b, err := l.ColorRGB(); err == nil {
- // Perceived brightness from: https://www.w3.org/TR/AERT/#color-contrast
- // In the future WCAG 3 APCA may be a better solution
- brightness := (0.299*r + 0.587*g + 0.114*b) / 255
- return brightness < 0.35
- }
- }
-
- return false
-}
-
 // Return scope substring of label name, or empty string if none exists
 func (l *Label) ExclusiveScope() string {
  if !l.Exclusive {

models/issues/label_test.go

@@ -22,15 +22,6 @@ func TestLabel_CalOpenIssues(t *testing.T) {
  assert.EqualValues(t, 2, label.NumOpenIssues)
 }
 
-func TestLabel_TextColor(t *testing.T) {
- assert.NoError(t, unittest.PrepareTestDatabase())
- label := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 1})
- assert.False(t, label.UseLightTextColor())
-
- label = unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 2})
- assert.True(t, label.UseLightTextColor())
-}
-
 func TestLabel_ExclusiveScope(t *testing.T) {
  assert.NoError(t, unittest.PrepareTestDatabase())
  label := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 7})

modules/templates/util_render.go

@@ -20,6 +20,7 @@ import (
  "code.gitea.io/gitea/modules/markup"
  "code.gitea.io/gitea/modules/markup/markdown"
  "code.gitea.io/gitea/modules/setting"
+ "code.gitea.io/gitea/modules/util"
 )
 
 // RenderCommitMessage renders commit message with XSS-safe and special links.
@@ -133,7 +134,9 @@ func RenderLabel(ctx context.Context, label *issues_model.Label) template.HTML {
  labelScope := label.ExclusiveScope()
 
  textColor := "#111"
- if label.UseLightTextColor() {
+ r, g, b := util.HexToRBGColor(label.Color)
+ // Determine if label text should be light or dark to be readable on background color
+ if util.UseLightTextOnBackground(r, g, b) {
  textColor = "#eee"
  }
 
@@ -150,34 +153,30 @@ func RenderLabel(ctx context.Context, label *issues_model.Label) template.HTML {
  scopeText := RenderEmoji(ctx, labelScope)
  itemText := RenderEmoji(ctx, label.Name[len(labelScope)+1:])
 
- itemColor := label.Color
- scopeColor := label.Color
- if r, g, b, err := label.ColorRGB(); err == nil {
- // Make scope and item background colors slightly darker and lighter respectively.
- // More contrast needed with higher luminance, empirically tweaked.
- luminance := (0.299*r + 0.587*g + 0.114*b) / 255
- contrast := 0.01 + luminance*0.03
- // Ensure we add the same amount of contrast also near 0 and 1.
- darken := contrast + math.Max(luminance+contrast-1.0, 0.0)
- lighten := contrast + math.Max(contrast-luminance, 0.0)
- // Compute factor to keep RGB values proportional.
- darkenFactor := math.Max(luminance-darken, 0.0) / math.Max(luminance, 1.0/255.0)
- lightenFactor := math.Min(luminance+lighten, 1.0) / math.Max(luminance, 1.0/255.0)
-
- scopeBytes := []byte{
- uint8(math.Min(math.Round(r*darkenFactor), 255)),
- uint8(math.Min(math.Round(g*darkenFactor), 255)),
- uint8(math.Min(math.Round(b*darkenFactor), 255)),
- }
- itemBytes := []byte{
- uint8(math.Min(math.Round(r*lightenFactor), 255)),
- uint8(math.Min(math.Round(g*lightenFactor), 255)),
- uint8(math.Min(math.Round(b*lightenFactor), 255)),
- }
-
- itemColor = "#" + hex.EncodeToString(itemBytes)
- scopeColor = "#" + hex.EncodeToString(scopeBytes)
- }
+ // Make scope and item background colors slightly darker and lighter respectively.
+ // More contrast needed with higher luminance, empirically tweaked.
+ luminance := util.GetLuminance(r, g, b)
+ contrast := 0.01 + luminance*0.03
+ // Ensure we add the same amount of contrast also near 0 and 1.
+ darken := contrast + math.Max(luminance+contrast-1.0, 0.0)
+ lighten := contrast + math.Max(contrast-luminance, 0.0)
+ // Compute factor to keep RGB values proportional.
+ darkenFactor := math.Max(luminance-darken, 0.0) / math.Max(luminance, 1.0/255.0)
+ lightenFactor := math.Min(luminance+lighten, 1.0) / math.Max(luminance, 1.0/255.0)
+
+ scopeBytes := []byte{
+ uint8(math.Min(math.Round(r*darkenFactor), 255)),
+ uint8(math.Min(math.Round(g*darkenFactor), 255)),
+ uint8(math.Min(math.Round(b*darkenFactor), 255)),
+ }
+ itemBytes := []byte{
+ uint8(math.Min(math.Round(r*lightenFactor), 255)),
+ uint8(math.Min(math.Round(g*lightenFactor), 255)),
+ uint8(math.Min(math.Round(b*lightenFactor), 255)),
+ }
+
+ itemColor := "#" + hex.EncodeToString(itemBytes)
+ scopeColor := "#" + hex.EncodeToString(scopeBytes)
 
  s := fmt.Sprintf("<span class='ui label scope-parent' title='%s'>"+
  "<div class='ui label scope-left' style='color: %s !important; background-color: %s !important'>%s</div>"+

modules/util/color.go

@@ -0,0 +1,65 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+package util
+
+import (
+ "fmt"
+ "math"
+ "strconv"
+ "strings"
+)
+
+// Check similar implementation in web_src/js/utils/color.js and keep synchronization
+
+// Return R, G, B values defined in reletive luminance
+func getLuminanceRGB(channel float64) float64 {
+ sRGB := channel / 255
+ if sRGB <= 0.03928 {
+ return sRGB / 12.92
+ }
+ return math.Pow((sRGB+0.055)/1.055, 2.4)
+}
+
+// Get color as RGB values in 0..255 range from the hex color string (with or without #)
+func HexToRBGColor(colorString string) (float64, float64, float64) {
+ hexString := colorString
+ if strings.HasPrefix(colorString, "#") {
+ hexString = colorString[1:]
+ }
+ // only support transfer of rgb, rgba, rrggbb and rrggbbaa
+ // if not in these formats, use default values 0, 0, 0
+ if len(hexString) != 3 && len(hexString) != 4 && len(hexString) != 6 && len(hexString) != 8 {
+ return 0, 0, 0
+ }
+ if len(hexString) == 3 || len(hexString) == 4 {
+ hexString = fmt.Sprintf("%c%c%c%c%c%c", hexString[0], hexString[0], hexString[1], hexString[1], hexString[2], hexString[2])
+ }
+ if len(hexString) == 8 {
+ hexString = hexString[0:6]
+ }
+ color, err := strconv.ParseUint(hexString, 16, 64)
+ if err != nil {
+ return 0, 0, 0
+ }
+ r := float64(uint8(0xFF & (uint32(color) >> 16)))
+ g := float64(uint8(0xFF & (uint32(color) >> 8)))
+ b := float64(uint8(0xFF & uint32(color)))
+ return r, g, b
+}
+
+// return luminance given RGB channels
+// Reference from: https://www.w3.org/WAI/GL/wiki/Relative_luminance
+func GetLuminance(r, g, b float64) float64 {
+ R := getLuminanceRGB(r)
+ G := getLuminanceRGB(g)
+ B := getLuminanceRGB(b)
+ luminance := 0.2126*R + 0.7152*G + 0.0722*B
+ return luminance
+}
+
+// Reference from: https://firsching.ch/github_labels.html
+// In the future WCAG 3 APCA may be a better solution.
+// Check if text should use light color based on RGB of background
+func UseLightTextOnBackground(r, g, b float64) bool {
+ return GetLuminance(r, g, b) < 0.453
+}

modules/util/color_test.go

@@ -0,0 +1,65 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+package util
+
+import (
+ "testing"
+
+ "github.com/stretchr/testify/assert"
+)
+
+func Test_HexToRBGColor(t *testing.T) {
+ cases := []struct {
+ colorString string
+ expectedR float64
+ expectedG float64
+ expectedB float64
+ }{
+ {"2b8685", 43, 134, 133},
+ {"1e1", 17, 238, 17},
+ {"#1e1", 17, 238, 17},
+ {"1e16", 17, 238, 17},
+ {"3bb6b3", 59, 182, 179},
+ {"#3bb6b399", 59, 182, 179},
+ {"#0", 0, 0, 0},
+ {"#00000", 0, 0, 0},
+ {"#1234567", 0, 0, 0},
+ }
+ for n, c := range cases {
+ r, g, b := HexToRBGColor(c.colorString)
+ assert.Equal(t, c.expectedR, r, "case %d: error R should match: expected %f, but get %f", n, c.expectedR, r)
+ assert.Equal(t, c.expectedG, g, "case %d: error G should match: expected %f, but get %f", n, c.expectedG, g)
+ assert.Equal(t, c.expectedB, b, "case %d: error B should match: expected %f, but get %f", n, c.expectedB, b)
+ }
+}
+
+func Test_UseLightTextOnBackground(t *testing.T) {
+ cases := []struct {
+ r float64
+ g float64
+ b float64
+ expected bool
+ }{
+ {215, 58, 74, true},
+ {0, 117, 202, true},
+ {207, 211, 215, false},
+ {162, 238, 239, false},
+ {112, 87, 255, true},
+ {0, 134, 114, true},
+ {228, 230, 105, false},
+ {216, 118, 227, true},
+ {255, 255, 255, false},
+ {43, 134, 133, true},
+ {43, 135, 134, true},
+ {44, 135, 134, true},
+ {59, 182, 179, true},
+ {124, 114, 104, true},
+ {126, 113, 108, true},
+ {129, 112, 109, true},
+ {128, 112, 112, true},
+ }
+ for n, c := range cases {
+ result := UseLightTextOnBackground(c.r, c.g, c.b)
+ assert.Equal(t, c.expected, result, "case %d: error should match", n)
+ }
+}

web_src/js/components/ContextPopup.vue

@@ -26,7 +26,7 @@
 <script>
 import $ from 'jquery';
 import {SvgIcon} from '../svg.js';
-import {useLightTextOnBackground} from '../utils.js';
+import {useLightTextOnBackground, hexToRGBColor} from '../utils/color.js';
 
 const {appSubUrl, i18n} = window.config;
 
@@ -77,7 +77,8 @@ export default {
  labels() {
  return this.issue.labels.map((label) => {
  let textColor;
- if (useLightTextOnBackground(label.color)) {
+ const [r, g, b] = hexToRGBColor(label.color);
+ if (useLightTextOnBackground(r, g, b)) {
  textColor = '#eeeeee';
  } else {
  textColor = '#111111';

web_src/js/features/repo-projects.js

@@ -1,5 +1,5 @@
 import $ from 'jquery';
-import {useLightTextOnBackground} from '../utils.js';
+import {useLightTextOnBackground, hexToRGBColor} from '../utils/color.js';
 
 const {csrfToken} = window.config;
 
@@ -190,7 +190,8 @@ export function initRepoProject() {
 }
 
 function setLabelColor(label, color) {
- if (useLightTextOnBackground(color)) {
+ const [r, g, b] = hexToRGBColor(color);
+ if (useLightTextOnBackground(r, g, b)) {
  label.removeClass('dark-label').addClass('light-label');
  } else {
  label.removeClass('light-label').addClass('dark-label');

web_src/js/utils.js

@@ -135,17 +135,3 @@ export function toAbsoluteUrl(url) {
  return `${window.location.origin}${url}`;
 }
 
-// determine if light or dark text color should be used on a given background color
-// NOTE: see models/issue_label.go for similar implementation
-export function useLightTextOnBackground(backgroundColor) {
- if (backgroundColor[0] === '#') {
- backgroundColor = backgroundColor.substring(1);
- }
- // Perceived brightness from: https://www.w3.org/TR/AERT/#color-contrast
- // In the future WCAG 3 APCA may be a better solution.
- const r = parseInt(backgroundColor.substring(0, 2), 16);
- const g = parseInt(backgroundColor.substring(2, 4), 16);
- const b = parseInt(backgroundColor.substring(4, 6), 16);
- const brightness = (0.299 * r + 0.587 * g + 0.114 * b) / 255;
- return brightness < 0.35;
-}

web_src/js/utils/color.js

@@ -0,0 +1,42 @@
+// Check similar implementation in modules/util/color.go and keep synchronization
+// Return R, G, B values defined in reletive luminance
+function getLuminanceRGB(channel) {
+ const sRGB = channel / 255;
+ return (sRGB <= 0.03928) ? sRGB / 12.92 : ((sRGB + 0.055) / 1.055) ** 2.4;
+}
+
+// Reference from: https://www.w3.org/WAI/GL/wiki/Relative_luminance
+function getLuminance(r, g, b) {
+ const R = getLuminanceRGB(r);
+ const G = getLuminanceRGB(g);
+ const B = getLuminanceRGB(b);
+ return 0.2126 * R + 0.7152 * G + 0.0722 * B;
+}
+
+// Get color as RGB values in 0..255 range from the hex color string (with or without #)
+export function hexToRGBColor(backgroundColorStr) {
+ let backgroundColor = backgroundColorStr;
+ if (backgroundColorStr[0] === '#') {
+ backgroundColor = backgroundColorStr.substring(1);
+ }
+ // only support transfer of rgb, rgba, rrggbb and rrggbbaa
+ // if not in these formats, use default values 0, 0, 0
+ if (![3, 4, 6, 8].includes(backgroundColor.length)) {
+ return [0, 0, 0];
+ }
+ if ([3, 4].includes(backgroundColor.length)) {
+ const [r, g, b] = backgroundColor;
+ backgroundColor = `${r}${r}${g}${g}${b}${b}`;
+ }
+ const r = parseInt(backgroundColor.substring(0, 2), 16);
+ const g = parseInt(backgroundColor.substring(2, 4), 16);
+ const b = parseInt(backgroundColor.substring(4, 6), 16);
+ return [r, g, b];
+}
+
+// Reference from: https://firsching.ch/github_labels.html
+// In the future WCAG 3 APCA may be a better solution.
+// Check if text should use light color based on RGB of background
+export function useLightTextOnBackground(r, g, b) {
+ return getLuminance(r, g, b) < 0.453;
+}

web_src/js/utils/color.test.js

@@ -0,0 +1,34 @@
+import {test, expect} from 'vitest';
+import {hexToRGBColor, useLightTextOnBackground} from './color.js';
+
+test('hexToRGBColor', () => {
+ expect(hexToRGBColor('2b8685')).toEqual([43, 134, 133]);
+ expect(hexToRGBColor('1e1')).toEqual([17, 238, 17]);
+ expect(hexToRGBColor('#1e1')).toEqual([17, 238, 17]);
+ expect(hexToRGBColor('1e16')).toEqual([17, 238, 17]);
+ expect(hexToRGBColor('3bb6b3')).toEqual([59, 182, 179]);
+ expect(hexToRGBColor('#3bb6b399')).toEqual([59, 182, 179]);
+ expect(hexToRGBColor('#0')).toEqual([0, 0, 0]);
+ expect(hexToRGBColor('#00000')).toEqual([0, 0, 0]);
+ expect(hexToRGBColor('#1234567')).toEqual([0, 0, 0]);
+});
+
+test('useLightTextOnBackground', () => {
+ expect(useLightTextOnBackground(215, 58, 74)).toBe(true);
+ expect(useLightTextOnBackground(0, 117, 202)).toBe(true);
+ expect(useLightTextOnBackground(207, 211, 215)).toBe(false);
+ expect(useLightTextOnBackground(162, 238, 239)).toBe(false);
+ expect(useLightTextOnBackground(112, 87, 255)).toBe(true);
+ expect(useLightTextOnBackground(0, 134, 114)).toBe(true);
+ expect(useLightTextOnBackground(228, 230, 105)).toBe(false);
+ expect(useLightTextOnBackground(216, 118, 227)).toBe(true);
+ expect(useLightTextOnBackground(255, 255, 255)).toBe(false);
+ expect(useLightTextOnBackground(43, 134, 133)).toBe(true);
+ expect(useLightTextOnBackground(43, 135, 134)).toBe(true);
+ expect(useLightTextOnBackground(44, 135, 134)).toBe(true);
+ expect(useLightTextOnBackground(59, 182, 179)).toBe(true);
+ expect(useLightTextOnBackground(124, 114, 104)).toBe(true);
+ expect(useLightTextOnBackground(126, 113, 108)).toBe(true);
+ expect(useLightTextOnBackground(129, 112, 109)).toBe(true);
+ expect(useLightTextOnBackground(128, 112, 112)).toBe(true);
+});