W3School TIY Editor

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

* {
  box-sizing: border-box;
}

.bg-img {
  /* 使用的图像 */
  background-image: url("/i/photo/wuhan.jpg");

min-height: 380px;

/* 中心对齐并适当缩放图像 */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
  position: relative;
}

/* 为表单容器添加样式 */
.container {
  position: absolute;
  right: 0;
  margin: 20px;
  max-width: 300px;
  padding: 16px;
  background-color: white;
}

/* 全宽输入框 */
input[type=text], input[type=password] {
  width: 100%;
  padding: 15px;
  margin: 5px 0 22px 0;
  border: none;
  background: #f1f1f1;
}

input[type=text]:focus, input[type=password]:focus {
  background-color: #ddd;
  outline: none;
}

/* 为提交按钮设置样式 */
.btn {
  background-color: #04AA6D;
  color: white;
  padding: 16px 20px;
  border: none;
  cursor: pointer;
  width: 100%;
  opacity: 0.9;
}

.btn:hover {
  opacity: 1;
}
</style>
</head>
<body>

<h2>背景图上的表单</h2>
<div class="bg-img">
  <form action="/action_page.php" class="container">
    <h1>Login</h1>

<label for="email"><b>Email</b></label>
    <input type="text" placeholder="Enter Email" name="email" required>

<label for="psw"><b>Password</b></label>
    <input type="password" placeholder="Enter Password" name="psw" required>

<button type="submit" class="btn">Login</button>
  </form>
</div>

<p>这个例子在响应式图像上创建了一个表单。请尝试调整浏览器窗口的大小，你会看到它始终会覆盖整个屏幕宽度，并且在所有屏幕尺寸上都能很好地缩放。</p>

</body>
</html>