W3School TIY Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body, html {
  height: 100%;
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

* {
  box-sizing: border-box;
}

.bg-image {
  /* 所用的图像 */
  background-image: url("/i/photo/programmer.jpg");
  
  /* 添加模糊效果 */
  filter: blur(8px);
  -webkit-filter: blur(8px);
  
  /* 全高 */
  height: 100%; 
  
  /* 将图像居中并适当地缩放 */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}

/* 将文本放置在页面/图像的中间 */
.bg-text {
  background-color: rgb(0,0,0); /* 回退颜色 */
  background-color: rgba(0,0,0, 0.4); /* 黑色半透明/可透视 */
  color: white;
  font-weight: bold;
  border: 3px solid #f1f1f1;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 2;
  width: 80%;
  padding: 20px;
  text-align: center;
}
</style>
</head>
<body>

<div class="bg-text">
  <h2>Blurred Background</h2>
  <h1 style="font-size:50px">I am Bill Gates</h1>
  <p>And I'm a Photographer</p>
</div>

</body>
</html>