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<!doctype html>
<html lang="en">
<head>
<title>Color contrast</title>
<meta content="width=device-width, initial-scale=1" name="viewport"/>
<meta content="index, follow" name="robots"/>
<meta content="text/css" http-equiv="content-style-type"/>
<meta content="application/javascript" http-equiv="content-script-type"/>
<meta content="en" http-equiv="Content-Language"/>
<meta content="application/xhtml+xml,charset=UTF-8" http-equiv="Content-Type"/>
<style type="text/css">
*:focus,
.inputfocus {
outline: 0.15em dashed #09f;
}
html {
font-family: sans-serif;
font-size : 10px;
}
h2 {
font-size: 3em;
margin : 0;
}
#controls,
#combinations {
background: #eee;
border : 0.1em solid #ccc;
margin : 0 0 2em;
padding : 2em;
}
#controls p strong {
display: block;
}
.textarea strong {
margin-bottom: 0.5em;
}
#controls p {
font-size: 1.4em;
margin : 1.5em 0 0;
}
#combinations p {
font-size: 1.4em;
}
.radio span {
display : inline-block;
margin-top: 0.5em;
width : 12em;
}
textarea {
height: 5em;
width : 100%;
}
select,
#scheme-name {
display : block;
min-width: 10em;
width : 25%;
}
#scheme-modify {
float : right;
margin-top: -2em;
}
#submit {
box-shadow : 0.05em 0.05em 0.1em #999;
display : block;
font-size : 1.4em;
font-weight: bold;
margin : 0 auto;
min-width : 20em;
width : 50%;
}
#error {
color: #d00;
}
#error strong {
display: inline;
}
#output {
font-family: monospace;
margin : 0;
padding : 0;
}
.light {
border: 0.1em solid #000;
color : #000;
}
.dark {
border: 0.1em solid #fff;
color : #fff;
}
.light p {
background: #fff;
border : 0.1em solid #000;
}
.dark p {
background: #000;
border : 0.1em solid #fff;
}
#output li ul {
margin-top: 1em;
}
#output li p {
padding : 0.25em;
text-align: center;
width : 6em;
}
#output .passfail {
width: 15em;
}
#output li {
display: block;
padding: 1em;
}
#output li li {
display : inline-block;
height : 8em;
margin : 0 1em 6em;
padding : 0;
text-align: center;
width : 8em;
}
#output li li p {
padding: 0.25em 0;
width : 100%;
}
#output .pass li p {
background : transparent;
border-style: none;
font-size : 1.4em;
}
#output .fail li p {
left : -0.1em;
position: relative;
top : 5.2em;
}
#output li li span {
display: block;
}
#output .exception {
display : block;
font-size : 1.2em;
height : auto;
text-align: left;
width : auto;
}
#output li .exception {
font-size: 1em;
}
#about {
max-width: 80em;
}
#aboutLink {
bottom : -2em;
float : right;
font-size: 1.4em;
margin : 0 1em 0 0;
position : relative;
}
#about p,
#about li {
font-size: 1.4em;
}
</style>
</head>
<body>
<h1><a href="http://www.w3.org/TR/WCAG20/">WCAG 2.0</a>
compliance color contrast</h1>
<p id="aboutLink"><a href="#about">About this tool</a></p>
<section id="controls">
<h2>Input controls</h2>
<p class="radio"><strong>WCAG compliance level</strong>
<span><input checked="checked" id="compliance-aa" name="compliance" type="radio" value="AA"/>
<label for="compliance-aa">AA</label></span>
<span><input id="compliance-aaa" name="compliance" type="radio" value="AAA"/>
<label for="compliance-aaa">AAA</label></span>
</p>
<p class="radio"><strong>Strictness</strong>
<span><input checked="checked" id="strictness-strict" name="strictness" type="radio" value="strict"/>
<label for="strictness-strict">All text</label></span>
<span><input id="strictness-weak" name="strictness" type="radio" value="weak"/>
<label for="strictness-weak">Large or Bold text</label></span>
</p>
<p class="radio"><strong>Failing Colors</strong>
<span><input checked="checked" id="fail-no" name="fail" type="radio" value="no"/>
<label for="fail-no">Hide failing colors</label></span>
<span><input id="fail-yes" name="fail" type="radio" value="yes"/>
<label for="fail-yes">Show failing colors</label></span>
</p>
<p class="textarea"><strong>Saved Color Schemes</strong>
<label for="color-scheme">Choose a color scheme or select
<em>new</em></label>
<select id="color-scheme"></select>
</p>
<p class="textarea"><strong>Modify Saved Color Schemes</strong>
<label for="scheme-name">Scheme Name</label>
<input id="scheme-name" type="text"/>
<button id="scheme-modify" type="button">Modify Saved Color
Schemes</button>
</p>
<p class="textarea"><strong>Input comma separated color hex codes,
example:
<em>#eee, #123def</em></strong>
<label for="color-input">Color codes</label>
<textarea id="color-input"></textarea>
</p>
<p><button id="submit" type="button">Show me contrasting colors</button></p>
<p id="error" style="display:none"></p>
</section>
<section id="combinations">
<h2>Available color combinations</h2>
<p>Minimum required color contrast:
<strong>4.5 : 1</strong></p>
<ul id="output"></ul>
</section>
<section id="about">
<div><h2>About this tool</h2>
<p>I found several color contrast tools online, but I found none written
in JavaScript and none that compared a plurality of colors. I tired of
watching my coworkers endlessly comparing colors from a limited list of
approved colors. There existed a need, so I built the tool.</p>
<p>The intention of this application is to create all contrast
comparisons for a given set of colors once. Since all colors are visible
in a pass or fail state it should be immediately clear what combinations
will be allowed. There is no need to even know what the acceptable rules
and limitations are if using a tool like this.</p>
<p>The following rules defined my approach:</p>
<ul>
<li><a href="http://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html">Rationale
for Chosen Contrast Ratios</a></li>
<li><a href="http://www.w3.org/TR/WCAG20/#relativeluminancedef">Relative
Luminance</a></li>
<li><a href="http://www.w3.org/TR/WCAG20/#contrast-ratiodef">Contrast
Ratio</a></li>
</ul>
<p>The solution is achieved by computing the relative luminance for a
given color and then comparing that color with the defined contrast
ratio. The mathmatical definitions are available in the W3C links
mentioned above. The JavaScript solution is available in the JavaScript
function
<em>luminance</em>
of this page's source code.</p>
<p>The reason why I had trouble finding similar tools written in
JavaScript is because JavaScript is bad at frational arithmetic. The
solution to this problem is to proportionally multiply all values by a
power of ten until you are far left of the decimal. A few extra digits
is recommended for extra precision.</p>
</div>
<div><h2>MIT License</h2>
<p>Copyright (c) 2015 Austin Cheney</p>
<p>Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:</p>
<p>The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.</p>
<p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.</p></div>
</section>
</body>
<script src="colorContrast.js" type="application/javascript"></script>
</html>
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