一、css渐变背景添加透明度opacity

css渐变背景经常会在项目开发中遇到，此时UI如果给出的是单一的渐变背景（没有背景透明度），这个我们会很快的写出代码，如下:

<div class="btn">这是一个按钮</div>

.btn {
  background: linear-gradient(to right, #8B78E6, #50A5A5);
  color: #fff;
  padding: 10px 20px;
  font-size: 16px;
  border-radius: 5px;
  border: none;
  cursor: pointer;
  transition: background 0.3s ease;
}

.btn:hover {
  background: linear-gradient(to right, #50A5A5, #8B78E6);
}

但偶尔的时候UI会给煎饼的背景色添加一个透明度，但是使用opacity属性会导致文本也会有透明度，接下来给出我的解决办法

.btn {
  position: relative;
  color: #fff;
  padding: 10px 20px;
  font-size: 16px;
  border-radius: 5px;
  border: none;
  cursor: pointer;
  transition: background 0.3s ease;
  z-index: 0;
}

.btn:hover {
  background: linear-gradient(to right, #50A5A5, #8B78E6);
}

.btn::after{
  position: absolute;
  z-index: -1;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  content: "";
  opacity: 0.3;
  background: linear-gradient(to right, #8B78E6, #50A5A5);
}

 二、css按钮添加渐变边框

1、使用border-image

.btn {
  border: 4px solid;
  border-image: linear-gradient(to right, #8f41e9, #578aef) 1;
}

/* 或者 */
.btn {
  border: 4px solid;
  border-image-source: linear-gradient(to right, #8f41e9, #578aef);
  border-image-slice: 1;
}

2、使用伪元素

<div class="border-box">
   <div class="content">
        这是一个使用伪元素实现渐变边框的按钮
   </div>
</div>

.border-box {
  border: 1px solid transparent;
  border-radius: 16px;
  position: relative;
  color: #F2B05E;
  background-color: #fff;
  background-clip: padding-box; /*important*/
}

.border-box::before {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  bottom: 0;
  z-index: -1;
  margin: -1px;
  border-radius: inherit; /*important*/
  background: linear-gradient(to right, #8F41E9, #578AEF);
}

3、使用单个元素background-clip、background-origin、background-image 

.border-box {
  border: 1px solid transparent;
  border-radius: 16px;
  color: #F2B05E;
  background-clip: padding-box, border-box;
  background-origin: padding-box, border-box;
  background-image: linear-gradient(to right, #fff,#fff), linear-gradient(90deg, #8F41E9, #578AEF);
}

background-clip 、background-origin属性添加了解释链接，没弄清的童鞋可以点击看下~

分享完毕~~