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gitea/web_src/js/utils/color.js
Hester Gong ea7954f069
Modify luminance calculation and extract related functions into single files (#24586)
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>
2023-05-10 11:19:03 +00:00

43 lines
1.6 KiB
JavaScript

// 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;
}