CSS画出的图

简单图形

矩形

div{
    width: 100px;
    height: 100px;
    background-color: red;
}

圆形

div{
    width: 100px;
    height: 100px;
    background-color: red;
    border-radius: %;
}

椭圆

【整个椭圆】

div{
    width: 100px;
    height: 50px;
    background-color: red;
    border-radius: %;
}

【半椭圆或半圆】

div{
  width: 100px;
  height: 100px;
  background:red;
  border-radius:50% /100% 100% 0 0 ;
}

【四分之一椭圆】

div{
  width: 100px;
  height: 100px;
  background:red;
  border-radius:100% 0 0 0 ;
}

三角形

【直角三角形】

div{
    width: ;
    height: ;
    border: 50px solid transparent;
    border-bottom-color: red;
}

【正三角形】

div{
    width: ;
    height: ;
    border: 50px solid transparent;
    border-width: 86.6px 50px;
    border-bottom-color: red;
}

平行四边形

【基本图形】

div{
    margin-left: 50px;
    width: 100px;
    height: 100px;
    background-color: red;
    transform: skew(30deg);
}

【改进版本】

　　上面的代码中，不仅形状发生了变形，内容也发生了变形。有两种方法改进

　　1、元素嵌套

.outer{
  margin-left:20px;
  width: 100px;
  height: 100px;
  background:red;
  transform:skewX(-30deg);
}
.inner{
   transform:skewX(30deg);
}
</style>
<div class="outer">
  <div class="inner">小火柴</div>
</div>

　　2、伪元素

　　把所有样式都应用到伪元素上，然后再对伪元素进行变形

div{
  position:relative;
  margin-left:20px;
  width: 100px;
  height: 100px;
  text-indent: 30px;
}
div::before{
  content:'';
  position:absolute;
  top: 0;right: 0;left: 0;bottom: 0;
  transform:skewX(-30deg);
  background:red;
  z-index:-1;
}

梯形

【基本版本】

div{
    width: 50px;
    border: 50px solid transparent;
    border-bottom-color: red;
}

【增强版本】

　　上面的代码虽然简单且巧妙，但无法在图形内容填充文本。下面是比较复杂的增强版本

div{
  height: 100px;
  width: 200px;
  line-height: 100px;
  position:relative;
  display:inline-block;
  text-align: center;
  color:white;
  padding: .5em 1em .35em;
}
div:before{
  content:'';
  position:absolute;
  top: 0;right: 0;bottom: 0;left: 0;
  z-index:-1;
  background:#58a;
  transform:scaleY(1.3) perspective(.5em) rotateX(5deg);
  transform-origin: bottom;
}

【梯形选项卡】

<style>
a{
  width: 120px;
  text-align: center;
  text-decoration: none;
  color:inherit;
  font-size: 20px
}
nav > a{
  position:relative;
  display:inline-block;
  padding:.3em .1em 0;
}
nav > a:before{
  content:'';
  position:absolute;
  top: 0;right: 0;left: 0;bottom: 0;
  z-index:-1;
  background:#ccc;
  border:1px solid black;
  border-radius: .5em .5em 0 0 ;
  box-shadow: 0 .15em white inset;

  transform:scaleY(1.3) perspective(.5em) rotateX(5deg);
  transform-origin: bottom;
}
</style>
<nav>
  <a href="#">HTML</a>
  <a href="#">CSS</a>
  <a href="#">Javascript</a>
</nav>

复杂图形

多角星

【五角星】

　　一个大三角形底部掏掉一个小三角形；两个前面的相同图形叠压

　　经计算，五角星的夹角为36度，若小三角形的侧边为a，则大三角形的侧边为2a(1+sin18)，两个三角形共同的底边为2a(sin54)

<div class="box">
　　<div class="in"></div>
　　<div class="in"></div>
</div>

.box{
    position: relative;
}
.in{
    margin-left: 100px;
    position: relative;
    width: 0px;
    border: 10px solid transparent;
    border-width: 249px 81px;
    border-bottom-color: red;
    position: absolute;
}
.in:after{
    content: "";
    position:absolute;
    border: 10px solid transparent;
    border-width: 59px 81px;
    border-bottom-color: white;
    top: 133px;
    left: -81px;
}
.in:last-child{
    top: 100px;
    left: -134px;
    transform: rotate(-73deg);
}

【六角星】

　　两个三角形叠压

div{
    position: relative;
    width: ;
    border: 50px solid transparent;
    border-width: 50px .4px;
    border-bottom-color: red;
}
div:after{
    position: absolute;
    content:"";
    width: ;
    border: 50px solid transparent;
    border-width: 50px .4px;
    border-top-color: red;
    top: 16px;
    left: -42px;
}

多边形

【六边形】

　　两个梯形拼接

div{
    position: relative;
    width: 50px;
    border: 50px solid transparent;
    border-bottom-color: red;
}
div:after{
    position: absolute;
    content:"";
    width: 50px;
    border: 50px solid transparent;
    border-top-color: red;
    top:50px;
    left: -50px;
}

【八边形】

.outer{
  width:100px;
  height: 100px;
  transform:rotate(45deg);
  overflow: hidden;
}
.inner{
  width:100%;
  height: 100%;
  transform:rotate(-45deg);
  background:red;
}

【菱形】

<style>
.outer{
  margin:50px 0 0 50px;
  width:100px;
  height: 100px;
  transform:rotate(45deg);
  overflow: hidden;
}
.inner{
  width:100%;
  height: 100%;
  transform:rotate(-45deg) scale(1.42);
  background:red;
}
</style>

桃心

　　创建一个方形div，分别用css控制div的两个伪元素平移到正方形相邻两边，圆形与边中点重合。最后将总的div旋转45度

<style>
div{
    display:inline-block;
    margin:50px;
    height: 100px;
    width: 100px;
    background-color: red;
    transform: rotate(-45deg);
}
div:before,div:after{
    display:block;
    content:"";
    width: 100px;
    height: 100px;
    background-color: red;
    border-radius: 50%;
    margin-top:-50%;
}
div:after{
    margin-left:50%;
}
</style>

<div></div>

切角效果

【单角】

background: linear-gradient(-45deg,transparent 5%,#58a 0);

【双角】

  background: linear-gradient(-45deg,transparent 5%,#58a 0) right,linear-gradient(45deg,transparent 5%,#58a 0) left;
  background-size:50% 100%;
  background-repeat:no-repeat;

【四角】

  background: linear-gradient(-135deg,transparent 5%,#58a 0) top right,linear-gradient(135deg,transparent 5%,#58a 0) top left,linear-gradient(-45deg,transparent 5%,#58a 0) bottom right,linear-gradient(45deg,transparent 5%,#58a 0) bottom left;
  background-size:50% 50%;
  background-repeat:no-repeat;

【弧形切角】

  background: radial-gradient(circle at top right,transparent 5%,#58a 0) top right,radial-gradient(circle at top left,transparent 5%,#58a 0) top left,radial-gradient(circle at bottom right,transparent 5%,#58a 0) bottom right,radial-gradient(circle at bottom left,transparent 5%,#58a 0) bottom left;
  background-size:50% 50%;
  background-repeat:no-repeat;

折角效果

background:linear-gradient(to left bottom,transparent 50%,rgba(0,0,0,0.4) 0) no-repeat 100% 0 /2em 2em,linear-gradient(-135deg,transparent 1.414em ,#58a 0);

饼图效果

　　饼图在网页中的运用极为普遍，比如简单的统计图表、进度指示器、定时器等

【静态效果】

<style>
@keyframes spin{
  to{transform: rotate(.5turn);}
}
@keyframes bg{50%{background:#655;}}
.pie{
  width: 100px;line-height: 100px;
  position:relative;
  background-color: yellowgreen;
  border-radius: 50%;
  color:transparent;
  text-align:center;
  background-image: linear-gradient(to right, transparent 50%,#655 0);
}
.pie:before{
  content:'';
  position:absolute;
  top: 0;left: 50%;
  width: 50%;height: 100%;
  border-radius: 0 100% 100% 0 /50%;
  background-color: inherit;
  transform-origin: left;
  animation: spin 50s linear infinite,bg 100s step-end infinite;
  animation-play-state:paused;
  animation-delay:inherit;
}
</style>
<div class="pie" style="animation-delay:-20s">20%</div>
<div class="pie" style="animation-delay:-90s">90%</div>

【动态效果】

<style>
@keyframes spin{
  to{transform: rotate(.5turn);}
}
@keyframes bg{50%{background:#655;}}

.pie{
  width: 100px;height: 100px;
  position:relative;
  background-color: yellowgreen;
  border-radius: 50%;
  background-image: linear-gradient(to right, transparent 50%,#655 0);
}
.pie:before{
  content:'';
  position:absolute;
  top: 0;left: 50%;
  width: 50%;height: 100%;
  border-radius: 0 100% 100% 0 /50%;
  background-color: inherit;
  transform-origin: left;
  animation: spin 3s linear infinite,bg 6s step-end infinite;
  animation-play-state: paused;
}
.pie:hover:before{
  animation-play-state: running;
}
</style>
<div class="pie"></div>

　　鼠标移入时，饼图发生移动

【SVG实现】

　　让圆形的周长接近于100，方便计算。r = 100/(2*PI) = 16

<style>
@keyframes fillup{to{stroke-dasharray:100 100;}}
svg{
  width: 100px;
  height: 100px;
  transform: rotate(-90deg);
  background: yellowgreen;
  border-radius: 50%;
}
circle{
  fill:yellowgreen;
  stroke:#655;
  stroke-width:32;
  stroke-dasharray: 0 100;
  animation: fillup 5s linear infinite;
}
</style>
<svg viewbox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
  <circle r=16 cx=16 cy=16></circle>
</svg>

最后

　　除了使用CSS画图之后，实现各种形状更简单的方法是使用clip-path路径裁剪样式

　　欢迎交流