转载自公众号前端印象
用到了css3中的:nth-child( n )选择器，以及:not(......)选择器和~兄弟选择器
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>微信朋友圈图片九宫格排版自适应（改编版）</title>
<style>
.pictures-adaptive {
display: flex;
flex-wrap: wrap;
}
.wrap {
position: relative;
overflow: hidden;
margin-bottom: 2%;
}
/* 3张图片 */
.wrap:nth-child(1):nth-last-child(3),
.wrap:nth-child(2):nth-last-child(2),
.wrap:nth-child(3):nth-last-child(1)
{
32%;
padding-bottom: 32%;
}
/* 间隔 */
.wrap:nth-child(2):nth-last-child(2),
.wrap:nth-child(3):nth-last-child(1)
{
margin-left: 2%;
}
.wrap:not(:nth-child(1):nth-last-child(1)) img {
position: absolute;
top: 0;
left: 0;
100%;
height: 100%;
object-fit: cover;
}
/* 2张图片 */
.wrap:nth-child(1):nth-last-child(2),
.wrap:nth-child(2):nth-last-child(1),
/* 4张图片 */
.wrap:nth-child(1):nth-last-child(4),
.wrap:nth-child(2):nth-last-child(3),
.wrap:nth-child(3):nth-last-child(2),
.wrap:nth-child(4):nth-last-child(1)
{
49%;
padding-bottom: 49%;
}
/* 每行的两张图片中间间隔2%的宽度 */
/* 2张图片 */
.wrap:nth-child(2):nth-last-child(1),
/* 4张图片 */
.wrap:nth-child(2):nth-last-child(3),
.wrap:nth-child(4):nth-last-child(1)
{
margin-left: 2%;
}
/* 5张以上图片 */
.wrap:nth-child(n + 5),
.wrap:nth-child(1):nth-last-child(n + 5),
.wrap:nth-child(1):nth-last-child(n + 5) ~ .wrap
{
32%;
padding-bottom: 32%;
}
.wrap:nth-child(n + 5):not(:nth-child(3n + 1)),
.wrap:nth-child(1):nth-last-child(n + 5) ~ .wrap:not(:nth-child(3n + 1))
{
margin-left: 2%;
}
</style>
</head>
<body>
<div class="pictures-adaptive">
<div class="wrap">
<img src="src1">
<img src="src2">
<img src="src3">
</div>
</div>
</body>
</html>