forked from AkkomaGang/akkoma-fe
cleanup, documentation, contrast taking alpha into account.
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2 changed files with 91 additions and 17 deletions
src
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@ -1,4 +1,4 @@
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import { rgb2hex, hex2rgb, getContrastRatio } from '../../services/color_convert/color_convert.js'
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import { rgb2hex, hex2rgb, getContrastRatio, worstCase } from '../../services/color_convert/color_convert.js'
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import ColorInput from '../color_input/color_input.vue'
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import ContrastRatio from '../contrast_ratio/contrast_ratio.vue'
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import OpacityInput from '../opacity_input/opacity_input.vue'
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@ -144,12 +144,13 @@ export default {
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}
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},
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previewTheme () {
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if (!this.preview.theme) return { colors: {}, opacity: {}, radii: {}, contrast: {} }
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if (!this.preview.theme) return { colors: {}, opacity: {}, radii: {} }
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return this.preview.theme
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},
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previewContrast () {
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if (!this.previewTheme.colors) return {}
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const colors = this.previewTheme.colors
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const opacity = this.previewTheme.opacity
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const hints = (ratio) => ({
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text: ratio.toPrecision(3) + ':1',
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// AA level, AAA level
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@ -160,16 +161,37 @@ export default {
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laaa: ratio >= 4.5
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})
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// fgsfds :DDDD
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const fgs = {
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text: hex2rgb(colors.text),
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panelText: hex2rgb(colors.panelText),
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btnText: hex2rgb(colors.btnText),
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topBarText: hex2rgb(colors.topBarText),
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link: hex2rgb(colors.link),
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topBarLink: hex2rgb(colors.topBarLink),
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}
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const bgs = {
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bg: hex2rgb(colors.bg),
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btn: hex2rgb(colors.btn),
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panel: hex2rgb(colors.panel),
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topBar: hex2rgb(colors.topBar)
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}
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const ratios = {
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bgText: getContrastRatio(hex2rgb(colors.bg), hex2rgb(colors.text)),
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bgLink: getContrastRatio(hex2rgb(colors.bg), hex2rgb(colors.link)),
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bgText: getContrastRatio(worstCase(bgs.bg, opacity.bg, fgs.text), fgs.text),
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bgLink: getContrastRatio(worstCase(bgs.bg, opacity.bg, fgs.link), fgs.link),
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panelText: getContrastRatio(hex2rgb(colors.panel), hex2rgb(colors.panelText)),
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// User Profile
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tintText: getContrastRatio(worstCase(bgs.bg, 0.5, fgs.panelText), fgs.text),
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btnText: getContrastRatio(hex2rgb(colors.btn), hex2rgb(colors.btnText)),
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panelText: getContrastRatio(worstCase(bgs.panel, opacity.panel, fgs.panelText), fgs.panelText),
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topBarText: getContrastRatio(hex2rgb(colors.topBar), hex2rgb(colors.topBarText)),
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topBarLink: getContrastRatio(hex2rgb(colors.topBar), hex2rgb(colors.topBarLink)),
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btnText: getContrastRatio(worstCase(bgs.btn, opacity.btn, fgs.btnText), fgs.btnText),
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topBarText: getContrastRatio(worstCase(bgs.topBar, opacity.topBar, fgs.topBarText), fgs.topBarText),
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topBarLink: getContrastRatio(worstCase(bgs.topBar, opacity.topBar, fgs.topBarLink), fgs.topBarLink)
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}
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return Object.entries(ratios).reduce((acc, [k, v]) => { acc[k] = hints(v); return acc }, {})
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@ -19,15 +19,21 @@ const rgb2hex = (r, g, b) => {
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return `#${((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1)}`
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}
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// https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
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// https://www.w3.org/TR/2008/REC-WCAG20-20081211/relative-luminance.xml
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// https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation
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const c2linear = (b) => {
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/**
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* Converts 8-bit RGB component into linear component
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* https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
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* https://www.w3.org/TR/2008/REC-WCAG20-20081211/relative-luminance.xml
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* https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation
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*
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* @param {Number} bit - color component [0..255]
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* @returns {Number} linear component [0..1]
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*/
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const c2linear = (bit) => {
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// W3C gives 0.03928 while wikipedia states 0.04045
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// what those magical numbers mean - I don't know.
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// something about gamma-correction, i suppose.
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// Sticking with W3C example.
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const c = b / 255
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const c = bit / 255
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if (c < 0.03928) {
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return c / 12.92
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} else {
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@ -35,18 +41,36 @@ const c2linear = (b) => {
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}
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}
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/**
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* Converts sRGB into linear RGB
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* @param {Object} srgb - sRGB color
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* @returns {Object} linear rgb color
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*/
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const srgbToLinear = (srgb) => {
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return 'rgb'.split('').reduce((acc, c) => { acc[c] = c2linear(srgb[c]); return acc }, {})
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}
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// https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
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// https://www.w3.org/TR/2008/REC-WCAG20-20081211/relative-luminance.xml
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/**
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* Calculates relative luminance for given color
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* https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
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* https://www.w3.org/TR/2008/REC-WCAG20-20081211/relative-luminance.xml
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*
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* @param {Object} srgb - sRGB color
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* @returns {Number} relative luminance
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*/
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const relativeLuminance = (srgb) => {
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const {r, g, b} = srgbToLinear(srgb)
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return 0.2126 * r + 0.7152 * g + 0.0722 * b
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}
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// https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
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/**
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* Generates color ratio between two colors. Order is unimporant
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* https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
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*
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* @param {Object} a - sRGB color
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* @param {Object} b - sRGB color
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* @returns {Number} color ratio
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*/
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const getContrastRatio = (a, b) => {
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const la = relativeLuminance(a)
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const lb = relativeLuminance(b)
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@ -55,6 +79,33 @@ const getContrastRatio = (a, b) => {
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return (l1 + 0.05) / (l2 + 0.05)
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}
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/**
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* This generates what "worst case" color would look like for transparent
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* segments. I.e. black with .2 alpha and pure-white background image
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* could make white text unreadable
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*
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* @param {Object} srgb - transparent color
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* @param {Number} alpha - color's opacity/alpha channel
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* @param {Boolean} white - use white "background" if true, black otherwise
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* @returns {Object} sRGB of resulting color
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*/
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const transparentWorstCase = (srgb, alpha, white = false) => {
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const bg = 'rgb'.split('').reduce((acc, c) => { acc[c] = Number(white) * 255; return acc }, {})
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return 'rgb'.split('').reduce((acc, c) => {
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// Simplified https://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
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// for opaque bg and transparent fg
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acc[c] = (srgb[c] * alpha + bg[c] * (1 - alpha))
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return acc
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}, {})
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}
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const worstCase = (bg, bga, text) => {
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if (bga === 1 || typeof bga === 'undefined') return bg
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// taken from https://github.com/toish/chromatism/blob/master/src/operations/contrastRatio.js
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const blackWorse = ((text.r * 299) + (text.g * 587) + (text.b * 114)) / 1000 <= 128
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return transparentWorstCase(bg, bga, !blackWorse)
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}
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const hex2rgb = (hex) => {
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const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex)
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return result ? {
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@ -84,5 +135,6 @@ export {
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hex2rgb,
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mixrgb,
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rgbstr2hex,
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getContrastRatio
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getContrastRatio,
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worstCase
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}
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