需求
工作中的需求，动态获取页面中的一个颜色值，应用到另一个元素的背景上，这样保持页面元素的颜色搭配比较统一。
难点
颜色值可以用户任意定义的，但是应用元素的文字字体颜色是固定白色的，这样如果用户定义的是浅色，那么应用元素的背景设置为浅色这个元素的文字就会看不清楚，如下
文字内容
方案
为了白色文字可以看清楚，考虑把浅色背景统一加深处理，已是深色不处理
效果如下(点击开始可随机显示浅色加深)：
浅色区域
深色区域
代码
复制以下代码粘贴进html文件可以直接运行
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>change color</title>
<style>
.colordivContainer{overflow: hidden;}
#colordiv{float:left;width:200px;height:100px;text-align:center;line-height:100px;font-size: 24px;font-weight: 700;color:#fff;background: #FFFF66; margin-right:10px;}
#changediv{float:left;width:200px;height:100px;text-align:center;line-height:100px;font-size: 24px;font-weight: 700;color:#fff;background: #d7d73e}
#isChange{float: left;}
.colorbtn{margin:5px;border-radius: 5px;}
</style>
</head>
<body>
<div id="changeColorContainer">
<div class="colordivContainer">
<div id="colordiv">浅色区域</div>
<div id="changediv">深色区域</div>
</div>
<button id="startColor" class="colorbtn">开始</button><button id="pauseColor" class="colorbtn">暂停</button>
</div>
<script>
//RGB颜色转化为16进制颜色
function colorHex(str) {
var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
var that = str;
if (/^(rgb|RGB)/.test(that)) {
var aColor = that.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",");
var strHex = "#";
for (var i = 0; i < aColor.length; i++) {
var hex = Number(aColor[i]).toString(16);
if (hex === "0") {
hex += hex;
}
strHex += hex;
}
if (strHex.length !== 7) {
strHex = that;
}
return strHex;
} else if (reg.test(that)) {
var aNum = that.replace(/#/, "").split("");
if (aNum.length === 6) {
return that;
} else if (aNum.length === 3) {
var numHex = "#";
for (var i = 0; i < aNum.length; i += 1) {
numHex += (aNum[i] + aNum[i]);
}
return numHex;
}
} else {
return that;
}
}
//16进制颜色转化为RGB颜色
function colorRgb(str) {
var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
var sColor = str.toLowerCase();
if (sColor && reg.test(sColor)) {
if (sColor.length === 4) {
var sColorNew = "#";
for (var i = 1; i < 4; i += 1) {
sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));
}
sColor = sColorNew;
}
//处理六位的颜色值
var sColorChange = [];
for (var i = 1; i < 7; i += 2) {
sColorChange.push(parseInt("0x" + sColor.slice(i, i + 2)));
}
return "rgb(" + sColorChange.join(",") + ")";
} else {
return sColor;
}
}
//变暗变亮主方法
function LightenDarkenColor (col, amt) {
var usePound = false;
if (col[0] == "#") {
col = col.slice(1);
usePound = true;
}
var num = parseInt(col, 16);
var r = (num >> 16) + amt;
if (r > 255) r = 255;
else if (r < 0) r = 0;
var b = ((num >> 8) & 0x00FF) + amt;
if (b > 255) b = 255;
else if (b < 0) b = 0;
var g = (num & 0x0000FF) + amt;
if (g > 255) g = 255;
else if (g < 0) g = 0;
return (usePound ? "#" : "") + String("000000" + (g | (b << 8) | (r << 16)).toString(16)).slice(-6);
}
//判断是否为亮色
function getContrastYIQ(hexcolor) {
var colorrgb = colorRgb(hexcolor);
var colors = colorrgb.match(/^rgb\((\d+),\s*(\d+),\s*(\d+)\)$/);
var red = colors[1];
var green = colors[2];
var blue = colors[3];
var brightness;
brightness = (red * 299) + (green * 587) + (blue * 114);
brightness = brightness / 255000;
if (brightness >= 0.5) {
return "light";
} else {
return "dark";
}
}
var startBtn = document.querySelector("#startColor"),
pauseBtn = document.querySelector("#pauseColor");
window.intervalSetColor = null;
startBtn.addEventListener("click",function(e){
if(intervalSetColor != null){
clearInterval(intervalSetColor);
}
intervalSetColor = setInterval(function(){
//获取随机颜色
var color = "",findColor = true;
while(findColor){
color = '#' +'0123456789abcdef'.split('').map(function(v,i,a){
return i>5 ? null : a[Math.floor(Math.random()*16)] }).join('');
if(getContrastYIQ(color) == "light"){
findColor = false;
}
}
//自定义变暗参数，< 0为变暗，>0为变亮
var amt = -40;
document.querySelector("#colordiv").style.backgroundColor = color;
document.querySelector("#changediv").style.backgroundColor = LightenDarkenColor(colorHex(color),amt); //调用核心方法处理浅色
},1000)
})
pauseBtn.addEventListener("click",function(e){
if(intervalSetColor != null){
clearInterval(intervalSetColor);
}
})
</script>
</body>
</html>
https://appsoftea.com/zh/js-color-change-darken-and-shallow/