66 lines
2.0 KiB
Go
66 lines
2.0 KiB
Go
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// 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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