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ea7954f069
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>
65 lines
2 KiB
Go
65 lines
2 KiB
Go
// Copyright 2023 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package util
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import (
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"fmt"
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"math"
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"strconv"
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"strings"
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)
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// Check similar implementation in web_src/js/utils/color.js and keep synchronization
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// Return R, G, B values defined in reletive luminance
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func getLuminanceRGB(channel float64) float64 {
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sRGB := channel / 255
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if sRGB <= 0.03928 {
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return sRGB / 12.92
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}
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return math.Pow((sRGB+0.055)/1.055, 2.4)
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}
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// Get color as RGB values in 0..255 range from the hex color string (with or without #)
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func HexToRBGColor(colorString string) (float64, float64, float64) {
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hexString := colorString
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if strings.HasPrefix(colorString, "#") {
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hexString = colorString[1:]
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}
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// only support transfer of rgb, rgba, rrggbb and rrggbbaa
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// if not in these formats, use default values 0, 0, 0
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if len(hexString) != 3 && len(hexString) != 4 && len(hexString) != 6 && len(hexString) != 8 {
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return 0, 0, 0
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}
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if len(hexString) == 3 || len(hexString) == 4 {
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hexString = fmt.Sprintf("%c%c%c%c%c%c", hexString[0], hexString[0], hexString[1], hexString[1], hexString[2], hexString[2])
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}
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if len(hexString) == 8 {
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hexString = hexString[0:6]
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}
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color, err := strconv.ParseUint(hexString, 16, 64)
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if err != nil {
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return 0, 0, 0
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}
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r := float64(uint8(0xFF & (uint32(color) >> 16)))
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g := float64(uint8(0xFF & (uint32(color) >> 8)))
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b := float64(uint8(0xFF & uint32(color)))
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return r, g, b
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}
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// return luminance given RGB channels
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// Reference from: https://www.w3.org/WAI/GL/wiki/Relative_luminance
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func GetLuminance(r, g, b float64) float64 {
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R := getLuminanceRGB(r)
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G := getLuminanceRGB(g)
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B := getLuminanceRGB(b)
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luminance := 0.2126*R + 0.7152*G + 0.0722*B
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return luminance
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}
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// Reference from: https://firsching.ch/github_labels.html
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// In the future WCAG 3 APCA may be a better solution.
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// Check if text should use light color based on RGB of background
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func UseLightTextOnBackground(r, g, b float64) bool {
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return GetLuminance(r, g, b) < 0.453
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}
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