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Modify luminance calculation and extract related functions into single files (#24586)

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Close #24508

Main changes:
As discussed in the issue

1. Change luminance calculation function to use [Relative
Luminance](https://www.w3.org/WAI/GL/wiki/Relative_luminance)
2. Move the luminance related functions into color.go/color.js
3. Add tests for both the files (Not sure if test cases are too many
now)

Before (tests included by `UseLightTextOnBackground` are labels started
with `##`):
https://try.gitea.io/HesterG/testrepo/labels

After:
<img width="1307" alt="Screen Shot 2023-05-08 at 13 37 55"
src="https://user-images.githubusercontent.com/17645053/236742562-fdfc3a4d-2fab-466b-9613-96f2bf96b4bc.png">
<img width="1289" alt="Screen Shot 2023-05-08 at 13 38 06"
src="https://user-images.githubusercontent.com/17645053/236742570-022db68e-cec0-43bb-888a-fc54f5332cc3.png">
<img width="1299" alt="Screen Shot 2023-05-08 at 13 38 20"
src="https://user-images.githubusercontent.com/17645053/236742572-9af1de45-fb7f-460b-828d-ba25fae20f51.png">

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Giteabot <teabot@gitea.io>
This commit is contained in:
Hester Gong 2023-05-10 19:19:03 +08:00 committed by GitHub
parent 0ca5adee16
commit ea7954f069
Signed by: GitHub
GPG Key ID: 4AEE18F83AFDEB23
10 changed files with 238 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
models/issues/label.go
View File

@ -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 {

9
models/issues/label_test.go
View File

@ -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})

53
modules/templates/util_render.go
View File

@ -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)
// 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)
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>"+

65
modules/util/color.go Normal file
View File

@ -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
}

65
modules/util/color_test.go Normal file
View File

@ -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)
}
}

5
web_src/js/components/ContextPopup.vue
View File

@ -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';

5
web_src/js/features/repo-projects.js
View File

@ -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');

14
web_src/js/utils.js
View File

@ -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;
}

42
web_src/js/utils/color.js Normal file
View File

@ -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;
}

34
web_src/js/utils/color.test.js Normal file
View File

@ -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);
});