css 的 conic-gradient 学习

偶然间在微信公众号奇舞周刊上看到了这篇文章《CSS Painting API》，算是对 conic-gradient的初次见面。
后来有空的时候，百度搜了一下，看了这篇文章《CSS神奇的conic-gradient圆锥渐变》后，对conic-gradient有了深刻的了解。

概述

conic-gradient：圆锥形渐变，它的两个兄弟line-gradient(线性渐变)、radial-gradient(径向渐变)，算是最早认识的渐变属性。

API

background: conic-gradient(pink, yellow); // basic demo

特点

圆锥渐变的起始点是图形中心，渐变方向以顺时针方向绕中心旋转实现渐变效果。

兼容性

根据 can i use，目前只在chrome 69及以上支持。

可以使用polyfill垫片库，解决兼容性问题。垫片库会根据css语法，生成对应的圆锥渐变图案，并且转化为 base64 代码。

// 需加入的js库
<script src="//cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<script src="//leaverou.github.io/conic-gradient/conic-gradient.js"></script>

案例1-颜色表盘

    <section class="color1"></section>
    <section class="color2"></section>

     /* 起始处与结尾处衔接不够自然 */
    .color1 {
      width: 200px;
      height: 200px;
      border-radius: 50%;
      background: conic-gradient(red, orange, yellow, green, teal, blue, purple)
    }
     /* 起始处与结尾处衔接不够自然，解决：在结尾加入开始的颜色 */
    .color2 {
      width: 200px;
      height: 200px;
      border-radius: 50%;
      background: conic-gradient(red, orange, yellow, green, teal, blue, purple, red);
    }

案例2-饼图

    <section class="pie"></section>

    .pie {
      width: 200px;
      height: 200px;
      border-radius: 50%;
      /* 百分比 写法一 */
       background: conic-gradient(pink 0, pink 30%, yellow 30%, yellow 70%, lime 70%, lime 100%); 
      /* 写法二 不支持 chrome69 */
      /* background: conic-gradient(pink 0 30%, yellow 0 70%, lime 0 100%); */
    }

案例3-菱形背景

    <section class="rhombus"></section>

    .rhombus {
      width: 200px;
      height: 200px;
      background: conic-gradient(#000 0, #000 12.5%, #fff 12.5%, #fff 37.5%, #000 37.5%, #000 62.5%, #fff 62.5%, #fff 87.5%, #000 87.5%,#000 0);
      border: 1px solid #000;
      background-size: 50px 50px;
    }

终极案例-仪表盘

<div class="bg">
        <div class="point"></div>
</div>

.bg {
        position: relative;
        margin: 50px auto;
        width: 400px;
        height: 400px;
        border-radius: 50%;
        background: conic-gradient(#f1462c 0%, #fc5d2c 12.4%, #fff 12.5%, #fff 12.5%, #fc5d2c 12.5%, #fba73e 24.9%, #fff 24.9%, #fff 25%, #fba73e 25%, #e0fa4e 37.4%, #fff 37.4%, #fff 37.5%, #e0fa4e 37.5%, #12dd7e 49.9%, #fff 49.9%, #fff 50%, #12dd7e 50%, #0a6e3f 62.4%, #fff 62.4%, #fff 62.5%);
        transform: rotate(-112.5deg);
        transform-origin: 50% 50%;
    }
      
    .bg::before {
        content: "";
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        width: 370px;
        height: 370px;
        border-radius: 50%;
        background: #fff;
    }
      
    .bg::after {
        content: "";
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        width: 320px;
        height: 320px;
        border-radius: 50%;
        background:
            radial-gradient(#fff 0%, #fff 25%, transparent 25%, transparent 100%),
            conic-gradient(#f1462c 0, #f1462c 12.5%, #fba73e 12.5%, #fba73e 25%, #e0fa4e 25%, #e0fa4e 37.5%, #12dd7e 37.5%, #12dd7e 50%, #0a6e3f 50%, #0a6e3f 62.5%, #fff 62.5%, #fff 100%);  
    }
      
    .point {
        position: absolute;
        width: 30px;
        height: 30px;
        transform: translate(-50%, -50%);
        left: 50%;
        top: 50%;
        background: radial-gradient(#467dc6 0%, #a4c6f3 100%);
        border-radius: 50%;
        z-index: 999;
    }
      
    .point::before {
        content: "";
        position: absolute;
        width: 5px;
        height: 350px;
        left: 50%;
        top: 50%;
        transform: translate(-50%, -50%) rotate(0);
        border-radius: 100% 100% 5% 5%;
        background: linear-gradient(
            180deg,
            #9bc7f6 0,
            #467dc6 50%,
            transparent 50%,
            transparent 100%
        );
        animation: pointerRotate 3s cubic-bezier(.93, 1.32, .89, 1.15) infinite;
    }
      
    @keyframes pointerRotate {
        50% {
            transform: translate(-50%, -50%) rotate(150deg);
        }
        100% {
            transform: translate(-50%, -50%) rotate(150deg);
        }
    }