用 CSS 实现三角形与平行四边形-守望者-AIR技术交流

破晓发表于 2016-8-15 14:46:51

用 CSS 实现三角形与平行四边形

<div>来源：http://div.io/topic/1238</div><div><blockquote style="margin: 32px 28px; padding-left: 14px; border-left-width: 3px; border-left-style: solid; border-left-color: rgb(204, 204, 204); line-height: 1.6; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px;">本文最初发布于我的个人博客：<a href="http://jerryzou.com/posts/use-css-to-paint-triangle-and-parallelogram/" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219);">咀嚼之味</a></blockquote><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">最近在逛某个技术网站的时候，感觉文章关键词上的样式好酷炫啊。于是我将那种写法照搬到了我的博客中，也许最近逛过我博客的小伙伴已经发现了它出现在哪儿了——分页的样式。来张截图：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/pagination.png!0.5" alt="分页样式的截图" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">你在首页的底部也可以看到这样一个分页栏；是不是看上去还不错？下面就来看看这是如何实现的吧~<h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">第一种方法：利用<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">border</code></h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">第一种方法是借助<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">border</code>属性 hack 出三角形，然后通过一个矩形拼接两个三角形最终制造出一个平行四边形。为什么使用<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">border</code>可以产生三角形呢？先来看看一张图片：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/triangle.png!0.5" alt="CSS triangle" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">看了图中的三个小图形的变化过程，你应该已经清楚了一半。其实 hack 出三角形只需要两个条件，第一，元素本身的长宽为0；其次，将不需要的部分通过 border-color 来设置隐藏。通过类似的方法，你还可以创造出梯形，上图中的三个图形的代码如下。（另附 <a href="http://codepen.io/jerryzou/pen/mJYJym" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219);">CodePen 示例</a>）<pre class="prettyprint lang-css prettyprinted" style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; padding: 6px 10px; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; border-radius: 3px; word-break: break-all; color: rgb(51, 51, 51); background-color: rgb(248, 248, 248);"><code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: 1.5; border: 0px none; border-radius: 0px; font-size: inherit; background: none;">#first {
width: 20px;
height: 20px;
border-width: 10px;
border-style: solid;
border-color: red green blue brown;
}

#second {
width: 0;
height: 0;
border-width: 10px;
border-style: solid;
border-color: red green blue brown;
}

#third {
width: 0;
height: 0;
border-width: 10px;
border-style: solid;
border-color: red transparent transparent transparent;
}</code></pre><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">接下来就要考虑如何拼接出一个平行四边形了。在<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">border</code>法中，它由三部分组成，分别是左三角形、矩形、右三角形。如果每次绘制平行四边形都要创建三个元素显然过于麻烦了，所以在这里<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">:before</code>和<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">:after</code>伪元素是个不错的选择。下面我们实现一下这样的效果：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/parallelogram.png!0.5" alt="three parallelogram" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">为了将三角形与矩形无缝拼接到一起，多处属性要保持一致，所以使用类似 Less, Sass, Stylus 等 CSS 预处理器来写这段代码会更容易维护，下面给出 Scss 版本的代码。（另附 <a href="http://codepen.io/jerryzou/pen/ZGNGWZ?editors=110" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219);">CodePen 链接</a>）<pre class="prettyprint lang-scss prettyprinted" style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; padding: 6px 10px; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; border-radius: 3px; word-break: break-all; color: rgb(51, 51, 51); background-color: rgb(248, 248, 248);"><code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: 1.5; border: 0px none; border-radius: 0px; font-size: inherit; background: none;">//三角形的宽高
$height: 24px;
$width: 12px;

//对平行四边形三部分的颜色进行赋值
@mixin parallelogram-color($color) {
background: $color;
&:before { border-color: transparent $color $color transparent; }
&:after { border-color: $color transparent transparent $color; }
}

//单个三角形的样式
@mixin triangle() {
content: '';
display: block;
width: 0;
height: 0;
position: absolute;
border-style: solid;
border-width: $height/2 $width/2;
top: 0;
}

//平行四边形的样式
.para {
display: inline-block;
position: relative;
padding: 0 10px;
height: $height;
line-height: $height;
margin-left: $width;
color: #fff;

&:after {
@include triangle();
right: -$width;
}

&:before {
@include triangle();
left: -$width;
}

@include parallelogram-color(red);
}</code></pre><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">需要注意的是，如果通过 <code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">$height</code>、<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">$width</code> 设置的三角形斜率太小或太大都有可能造成渲染出锯齿，所以使用起来要多多测试一下不同的宽高所得到的视觉效果如何。<h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">第二种方法：利用<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">transform</code></h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">使用<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">transform</code>来实现平行四边形的方法是我在逛<a href="http://www.alitrip.com/" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219);">去啊</a>的时候看到的，效果大概是这个样子：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/qua_parallelogram.png!0.5" alt="去啊中的平行四边形" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">看到之后觉得好神奇啊，原来还可以只有平行四边形的外轮廓。（因为方法一只能创造填充效果的平行四边形）实现起来非常简单，主要是借助了<code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">transform: skew(...)</code>，下面就来看看源码吧。<pre class="prettyprint lang-html prettyprinted" style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; padding: 6px 10px; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; border-radius: 3px; word-break: break-all; color: rgb(51, 51, 51); background-color: rgb(248, 248, 248);"><code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: 1.5; border: 0px none; border-radius: 0px; font-size: inherit; background: none;"><style>
.city {
display: inline-block;
padding: 5px 20px;
border: 1px solid #44a5fc;
color: #333;
transform: skew(-20deg);
}
</style>

<div class="city">上海</div></code></pre><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">于是我们得到了这样的效果：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/shanghai_skew.png!0.5" alt="skew shanghai" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">看到图片的你一定是这样想的：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/damn.gif" alt="坑爹呢这是" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">别着急嘛，我们的确是把整个 div 进行了歪曲，导致中间的文字也是倾斜的，而这显然不是我们所要的效果。所以我们需要加一个内层元素，并对内层元素做一次逆向的歪曲，从而得到我们想要的效果：<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><img src="http://jerryblog-image.b0.upaiyun.com/blog/posts/shanghai_normal.png!0.5" alt="normal shanghai" style="max-width: 50em; margin-top: 1em; margin-bottom: 1em;"><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">实现代码如下，另附 <a href="http://codepen.io/jerryzou/pen/BNeNwV?editors=110" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219);">CodePen 示例</a><pre class="prettyprint lang-html prettyprinted" style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; padding: 6px 10px; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; border-radius: 3px; word-break: break-all; color: rgb(51, 51, 51); background-color: rgb(248, 248, 248);"><code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: 1.5; border: 0px none; border-radius: 0px; font-size: inherit; background: none;"><style>
.city {
display: inline-block;
padding: 5px 20px;
border: 1px solid #44a5fc;
color: #333;
transform: skew(-20deg);
}

.city div {
transform: skew(20deg);
}
</style>

<div class="city">
<div>上海</div>
</div></code></pre><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">总结</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">第一种方法使用 <code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">border</code> 属性 hack 出三角形，并通过对三个元素进行拼接最终实现了平行四边形；而第二种方法则通过 <code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: normal; margin-right: 0.25em; margin-left: 0.25em; padding-right: 0.4em; padding-left: 0.4em; border: 1px solid rgb(221, 221, 221); border-radius: 3px; background-color: rgb(248, 248, 248);">transform: skew</code> 来得到平行四边形。总体来说，第二种方法相对于第一种代码量小得多，而且也很好理解。唯一的不足是无法构造像本站的分页中所使用的梯形。希望本文对各位有所帮助。<h3 style="font-size: 20px; counter-reset: subsection 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">UPDATE</h3><ul style="padding-left: 30px; margin-top: 14px; margin-bottom: 14px; list-style-type: square; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><li>2015.8.18, <a href="http://weibo.com/fouber" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219); border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: transparent;">@前端农民工</a> 给出了一个 CSS-Tricks 的<a href="https://css-tricks.com/examples/ShapesOfCSS/" target="_blank" style="text-decoration: none; color: rgb(49, 135, 219); border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: transparent; margin-left: 0.25em;">链接</a>，是关于各种用 CSS 绘制几何图形的方法，浅显易懂，推荐大家看看！</li></ul></div>

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用 CSS 实现三角形与平行四边形