css vertically centering a fixed positioning div

I have the following HTML for a sort-of lightbox project.

<div id="lightbox">
  <img id="image" src="" />
</div>

that is using the following 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;
}

To have the image always in the horizontal center, I am simply using text-align:center on the wrapper div, so I am 100% sure it will be correct.

I am facing problems with the vertical centering and I am using a workaround of simply setting the top value in the #lightbox properties.

As you can see the height of the image is known, so it is easily doable in jQuery but I am looking for a pure CSS solution.

Any ideas? Thanks.

Solution 1:

The best solution I've seen for both vertically and horizontally centering a position: fixed div is:

position: fixed;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);

Fiddle and source. You don't need to know the dimensions of the div and it doesn't require any container divs. The centered div's width can even be a percentage (which was what I was looking for when I found this solution).

Solution 2:

Alternatively, you could try this (only works if you know the height of the image):

#image{
position:relative;
height:600px;
top: 50%;
margin-top: -300px; /* minus half the height */
border:1px solid grey;
}

Solution 3:

Here are couple SASS mixins I'm using... I hope this is going to help someone:

// 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%);
}

Solution 4:

Use a combo of CSS3's viewport units and calc( ) to center a lightbox without the risk of blurring text due to hardware acceleration. This solution is also responsive. Convert the formula margin-top = -height / 2 from fixed units to viewport units

/* 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 );
}

JSFiddle

More information on relative length units and calc( ):

https://developer.mozilla.org/en-US/docs/Web/CSS/length
https://developer.mozilla.org/en-US/docs/Web/CSS/calc

Detailed Example

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>

css vertically centering a fixed positioning div

Solution 1:

Solution 2:

Solution 3:

Solution 4:

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