scss mixin

/* 图片居中显示 */
@mixin img-box($width,$height:$width,$border:none){
width:$width;
height:$height;
text-align:center;
@if $border==none {
line-height: $height;
img{
vertical-align: middle;
max-width: 100%;
max-height: 100%;
}
}
@else {
border: $border;
line-height: ($height - 3);
img{
vertical-align: middle;
max-width: $width - 2;
max-height: $height - 2;
}

}

}

使用：
.img-box {
@include img-box(230px);
margin-right: 100px;
}
参数如果不指定默认值，则必须传参
$width - 2 运算符前后必须有空格，否则解析出错