我有以下 HTML 用于某种灯箱项目。
<div id="lightbox">
<img id="image" src="" />
</div>
即使用以下 CSS：
#lightbox{
display:none;
position:fixed;
width:100%;
text-align:center;
z-index:600;
cursor:pointer;
left:0;
top:100px;
}
#image{
position:relative;
height:600px;
border:1px solid grey;
}
为了让图像始终处于水平中心，我只是在包装器 div 上使用 text-align:center，所以我 100% 确定它是正确的。
我遇到了垂直居中的问题，我正在使用一种解决方法，即在#lightbox 属性中简单地设置顶部值。
如您所见，图像的高度是已知的，因此在 jQuery 中很容易实现，但我正在寻找一个纯 CSS 解决方案。
有任何想法吗？谢谢。
或者，您可以尝试这个（仅当您知道图像的高度时才有效）：
#image{
position:relative;
height:600px;
top: 50%;
margin-top: -300px; /* minus half the height */
border:1px solid grey;
}
这是我正在使用的几个 SASS 混合...我希望这会对某人有所帮助：
// vertically centers as relative
@mixin vertical-align {
position: relative;
top: 50%;
-webkit-transform: translateY(-50%);
-ms-transform: translateY(-50%);
transform: translateY(-50%);
}
// vertically centers the element as absolute
@mixin vertical-center {
position: absolute;
top: 50%;
-webkit-transform: translateY(-50%);
-ms-transform: translateY(-50%);
transform: translateY(-50%);
}
// horizontally centers the element as absolute
@mixin horizontal-center {
position: absolute;
left: 50%;
-webkit-transform: translateY(-50%);
-ms-transform: translateY(-50%);
transform: translateY(-50%);
}
// absolutely centers the element inside of its first non-static parent
@mixin absolute-center {
position: absolute;
top: 50%;
left: 50%;
-webkit-transform: translateY(-50%);
-ms-transform: translateY(-50%);
transform: translateY(-50%);
}
使用 CSS3 的视口单元和 calc( ) 的组合来使灯箱居中，而不会有由于硬件加速而导致文本模糊的风险。此解决方案也是响应式的。将公式
margin-top = -height / 2从固定单位转换为视口单位
/* Overlay */
body::after
{
position: fixed;
z-index: 19000;
top: 0;
left: 0;
display: block;
width: 100%;
height: 100%;
content: ' ';
opacity: .2;
background-color: #000;
}
/* Lightbox */
.lightbox
{
position: fixed;
z-index: 15;
top: 50%;
width: 90vw;
height: 90vh;
margin: 0 5vw;
margin-top: calc(-90vh / 2 );
}
有关相对长度单位和 calc( ) 的更多信息：
详细示例
body {
margin: 0;
}
/* The Overlay */
body::after {
position: fixed;
z-index: 14;
top: 0;
left: 0;
display: block;
width: 100%;
height: 100%;
content:' ';
opacity: .5;
background-color: #000;
}
/* The Lightbox */
.lightbox{
position: fixed;
z-index: 15;
top: 50%;
width: 60vw;
height: 60vh;
margin: 0 20vw;
margin-top: calc(-60vh / 2);
background:#fff;
border: 1px solid white;
border-radius: 5px;
overflow:hidden;
box-shadow: 0px 0px 20px 0px rgba(0, 0, 0, 0.8);
}
/* Bonus: responsive and centered image */
.lightbox h1 {
box-shadow: 0px 0px 20px 0px rgba(0, 0, 0, 0.8);
position: relative;
padding-left: 1em;
font-family: sans-serif;
color: #E2E8F2;
}
.highlight
{
color: #4E2622;
}
.lightbox img {
max-width: 120%;
height: auto;
position:absolute;
top: 50%;
left: 50%;
-webkit-transform: translate(-50%, -50%);
-moz-transform: translate(-50%, -50%);
-ms-transform: translate(-50%, -50%);
-o-transform: translate(-50%, -50%);
transform: translate(-50%, -50%);
}<div class="lightbox">
<img src="https://pbs.twimg.com/media/CMSrIg_XAAAQU3a.jpg:large">
<h1><span class="highlight">Sono</span> Neko その猫</h1>
</div>
<h1>Leave dead animals as gifts</h1>
<h3>Meowwww missing until dinner time</h3>
<p>Cat ipsum dolor sit amet, vommit food and eat it again. Find something else more interesting favor packaging over toy yet hide at bottom of staircase to trip human or intently stare at the same spot, but poop in litter box, scratch the walls attack feet ears back wide eyed. Scratch leg; meow for can opener to feed me. Where is my slave? i'm getting hungry purr for no reason or eat a plant, kill a hand eat a plant, kill a hand. Where is my slave? i'm getting hungry jump around on couch, meow constantly until given food, , so chase dog then run away yet stick butt in face, for poop on grasses for rub face on owner, under the bed. Brown cats with pink ears meow destroy the blinds why must they do that, and see owner, run in terror. Meowing non stop for food play time, yet stand in front of the computer screen get video posted to internet for chasing red dot poop in litter box, scratch the walls. Destroy couch leave dead animals as gifts why must they do that, for find something else more interesting hopped up on catnip sleep in the bathroom sink. Kitty power! pooping rainbow while flying in a toasted bread costume in space eat grass, throw it back up and spread kitty litter all over house. I like big cats and i can not lie. Under the bed brown cats with pink ears loves cheeseburgers has closed eyes but still sees you yet chase red laser dot. Claw drapes drink water out of the faucet and behind the couch refuse to leave cardboard box but hunt anything that moves. Rub face on owner favor packaging over toy yet play time. Hide when guests come over love to play with owner's hair tie. Purr for no reason make meme, make cute face eat a plant, kill a hand all of a sudden cat goes crazy, or stare at the wall, play with food and get confused by dust for hate dog love to play with owner's hair tie. Sleep on keyboard eat grass, throw it back up but hopped up on catnip make meme, make cute face. Pooping rainbow while flying in a toasted bread costume in space. Chase imaginary bugs destroy the blinds claws in your leg for hack up furballs. I am the best chase laser but i am the best yet meow all night having their mate disturbing sleeping humans and hunt by meowing loudly at 5am next to human slave food dispenser. Destroy the blinds. Eat a plant, kill a hand run in circles, and chew iPad power cord, and rub face on everything, and sit in box mark territory, so ignore the squirrels, you'll never catch them anyway. Present belly, scratch hand when stroked nap all day, and spot something, big eyes, big eyes, crouch, shake butt, prepare to pounce destroy couch, but put toy mouse in food bowl run out of litter box at full speed .</p>如果您希望图像具有流体大小，可以使用视图的高度作为参考：
#img {
position: relative; /* or absolute or fixed depending on your needs */
top: 50%;
height: 80vh;
margin-top: -40vh; /* minus half the height */
}
为我解决的问题是从那里添加一个具有这些属性的空超级父级 -> 每个子级或子级都将垂直和水平居中。
如果您只需要水平/垂直删除我在代码注释中写的不必要的属性。
CSS：
.page-area{
position: fixed;
z-index: 5;/*not must but usually fixed elements require to be top*/
height: 100%;
width: 100%;
display: flex;
justify-content: center;/*define the horizontally centering*/
align-items: center;/*define the vertically centering*/
}
HTML：
<div class = "page-area">
<div>My centered element/s</div>
</div>
要使项目垂直居中，您需要以下 2 个 css 属性：
display:table-cell;
vertical-align:middle;
示例：http: //jsfiddle.net/yjv94/