我想在用户点击它时显示完整的图像，但不移动所有内容，模拟一个在屏幕上显示完整图像的模态，而不是其他图像，就像当你点击Facebook图片帖子时。
我已经尝试过z-index，使用position但我无法使其工作。
是的，我只需要使用HTML和CSS。
.container-fluid {
padding: 0em 10em;
}
.h1 {
margin-bottom: 35px;
box-shadow: 0 5px 5px -5px #333;
color: #70aeb6;
}
a.photo-container>img {
margin-bottom: 50px;
}
a.photo-container {
text-decoration: none;
}
a.photo-container:active>img {
width: 100%;
height: 100%;
}<!DOCTYPE html>
<html lang="es-MX">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<link rel="shortcut icon" type="image/png" href="https://via.placeholder.com/16x16" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link rel="stylesheet" href="css/styles.css">
<title>Gallery</title>
</head>
<div class="container-fluid">
<div class="h1 text-center">
Classmates gallery
</div>
<div class="d-inline">
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
</div>
</div>
</html>也许尝试使用 css 转换。下面是一个示例，请尝试将这些行添加到代码中：
a.photo-container {
transition: transform .2s ease-in-out;
}
a.photo-container:active>img {
transform: scale(1.4);
}
.container-fluid {
padding: 0em 10em;
}
.h1 {
margin-bottom: 35px;
box-shadow: 0 5px 5px -5px #333;
color: #70aeb6;
}
a.photo-container>img {
margin-bottom: 50px;
transition: transform .2s ease-in-out;
}
a.photo-container {
text-decoration: none;
position: relative;
display: inline-block;
}
a.photo-container:active>img {
transform: scale(1.4);
}<!DOCTYPE html>
<html lang="es-MX">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<link rel="shortcut icon" type="image/png" href="https://via.placeholder.com/16x16" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link rel="stylesheet" href="css/styles.css">
<title>Gallery</title>
</head>
<div class="container-fluid">
<div class="h1 text-center">
Classmates gallery
</div>
<div class="d-block">
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
<a href="#" class="photo-container">
<img src="https://via.placeholder.com/300x200">
</a>
</div>
</div>
</html>