色入力:コントラストチェッカー

InputColorコントロールを使用して色を選択し、 Colorクラスを使用して色を検査し、アクセシビリティ標準に準拠するのに十分なコントラストを提供しているかどうかを確認します。

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import './styles.css'; // import { InputColor } from '@mescius/wijmo.input'; import { Color, toggleClass, format } from '@mescius/wijmo'; // document.readyState === 'complete' ? init() : window.onload = init; // function init() { // create InputColor controls let cpFore = new InputColor('#icFore', { value: 'black', valueChanged: updateRatio }); let cpBack = new InputColor('#icBack', { value: 'white', valueChanged: updateRatio }); updateRatio(); // update the contrast ratio when the colors change function updateRatio() { // get lightness ratio let lFore = getRelativeLuminance(cpFore.value); let lBack = getRelativeLuminance(cpBack.value); let ratio = (Math.max(lFore, lBack) + .05) / (Math.min(lFore, lBack) + 0.05); // show sample text let sample = document.querySelectorAll('.sample'); for (let i = 0; i < sample.length; i++) { let style = sample[i].style; style.color = cpFore.value; style.background = cpBack.value; } // show the result let e = document.getElementById('ratio'); e.innerHTML = format('<b>{ratio:g1}</b>:1', { ratio: ratio }); e.style.borderColor = ratio < 7 ? 'whitesmoke' : 'darkgreen'; pass('aa-normal', ratio >= 4.5); pass('aa-large', ratio >= 3); pass('aaa-normal', ratio >= 7); pass('aaa-large', ratio >= 4.5); } function pass(id, pass) { let e = document.getElementById(id); e.textContent = pass ? 'Pass' : 'Fail'; toggleClass(e, 'fail', !pass); } // https://developer.mozilla.org/en-US/docs/Web/Accessibility/Understanding_Colors_and_Luminance function getRelativeLuminance(color) { let c = new Color(color); let r = getChannel(c.r); let g = getChannel(c.g); let b = getChannel(c.b); return (r * 0.2126 + g * 0.7152 + b * 0.0722); } function getChannel(rgb) { rgb /= 255; return rgb <= 0.03928 ? rgb / 12.92 : Math.pow((rgb + 0.055) / 1.055, 2.4); } }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo InputColor Contrast Checker</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.21.5/system.src.js" integrity="sha512-skZbMyvYdNoZfLmiGn5ii6KmklM82rYX2uWctBhzaXPxJgiv4XBwJnFGr5k8s+6tE1pcR1nuTKghozJHyzMcoA==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app'); </script> </head> <body> <div class="container-fluid"> <h1> コントラストチェッカー </h1> <div class="row"> <div class="col-md-4"> <h3> 前景色 </h3> <div id="icFore"></div> <h3> 背景色 </h3> <div id="icBack"></div> </div> <div class="col-md-4"> <h3> コントラスト比 </h3> <div id="ratio"></div> <h3> 結果 </h3> <p class="sample"> 通常のテキスト </p> <p> WCAG AA: <span id="aa-normal" class="result"></span> WCAG AAA: <span id="aaa-normal" class="result"></span> </p> <p class="sample large"> 大きいテキスト </p> <p> WCAG AA: <span id="aa-large" class="result"></span> WCAG AAA: <span id="aaa-large" class="result"></span> </p> </div> </div> <h3> 説明 </h3> <p> WCAG 2.0のレベルAAでは、通常のテキストでは少なくとも4.5:1、大きなテキストでは3:1のコントラスト比が必要です。 </p> <p> WCAG 2.1では、グラフィックスとユーザーインターフェイスコンポーネント(フォーム入力ボーダーなど)に対して少なくとも3:1のコントラスト比が必要です。 </p> <p> WCAGのレベルAAAでは、通常のテキストでは少なくとも7:1、大きなテキストでは4.5:1のコントラスト比が必要です。 </p> <p> 詳細については、 <a href="https://developer.mozilla.org/en-US/docs/Web/Accessibility/Understanding_Colors_and_Luminance" target="_blank" rel="noopener noreferrer"> Understanding Colors and Luminance </a>を参照してください。 </p> </div> </body> </html>
#sample { padding: 12px; font-style: bold; } #ratio { font-size: 200%; padding: 12px; font-style: bold; text-align: center; border-radius: 4px; border: 2px solid whitesmoke; } .sample { padding: 6px; margin: 6px 0; border: 2px solid whitesmoke; } .large { font-size: 14pt; font-weight: bold; } .result { font-weight: bold; margin-right: 2em; padding: 3px 6px; border-radius: 6px; color: white; background: darkgreen; } .result.fail { background: darkred; }
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