I think this is a math question more than anything else, who knew I'd need to know geometry for CSS.
I have an upright background image inside a rotated container. The image has to cover the container perfectly, and the container itself needs be stuck to the wall so that the user doesn't see the rotation on the side. I want to have dynamic control over the sizing of this element, so I would like everything to be done with percentages.
The blue line is the "wall".
Since the image is upright it has to be quite a bit bigger than its container. I found the formula for this here. That's what it looks like:
So the dimensions are in percentages, what I haven't figured out how to calculate is the various positionings. Without the pixel values I added it looks like this:
So how do I calculate these distances?
Here is my CodePen, it's in SCSS, all the math is done in the code.
body {
padding: 2em 5em;
}
.wrapper {
border-left: 3px solid blue;
}
.wrapper .container {
opacity: 0.7;
width: 300px;
background-color: red;
border-radius: 0 40px 40px 0;
overflow: hidden;
transform: rotate(10deg);
margin-left: -42px;
}
.wrapper .container .sizing-wrapper {
width: 100%;
padding-top: 150%;
position: relative;
}
.wrapper .container .img {
position: absolute;
top: 0;
left: 0;
background: url("http://placekitten.com/300/450") no-repeat right top;
background-size: cover;
height: 110.0573842629%;
width: 124.5280657351%;
transform: rotate(-10deg) ranslateY(-31px) translateX(-32px);
}
<div class="wrapper">
<div class="container">
<div class="sizing-wrapper">
<div class="img"></div>
</div>
</div>
</div>
I shared my question on Facebook and Amit Sheen came up with a solution I initially dismissed of using transform-origin. Now that I've seen it work I'm not sure why I thought it wouldn't.
The fixed CodePen
To make sure the container is cut by the wall at the right place we need to rotate it from the top left corner by using transform-origin: 0 0.
And we need to center the image inside the container:
.img {
top: 50%;
left: 50%;
transform: rotate(-$deg) translateY(-50%) translateX(-50%);
transform-origin: 0 0;
}
I'm still curious what the mathematical solution to my question is, because I'm sure there is one, but for actual use this is probably better...
body {
padding: 2em 5em;
}
.wrapper {
border-left: 3px solid blue;
}
.wrapper .container {
opacity: 0.7;
width: 300px;
background-color: red;
border-radius: 0 40px 40px 0;
overflow: hidden;
transform: rotate(10deg);
transform-origin: 0 0;
}
.wrapper .sizing-wrapper {
width: 100%;
padding-top: 150%;
position: relative;
}
.wrapper .img {
position: absolute;
top: 50%;
left: 50%;
background: url("http://placekitten.com/300/450") no-repeat right top;
background-size: cover;
height: 110.0573842629%;
width: 124.5280657351%;
transform: rotate(-10deg) translateY(-50%) translateX(-50%);
transform-origin: 0 0;
}
<div class="wrapper">
<div class="container">
<div class="sizing-wrapper">
<div class="img"></div>
</div>
</div>
</div>
I have made a footer in Photoshop looking like this:
As you can see, the footer here is slightly arced all the way across. I have tried doing something with border-radius, but that almost only targets the edge, which makes the arc more curved in the edges, and not even receiving the effect of a subtle arced footer as seen in the image.
Is there an easy CSS way to do this, or do I need some JavaScript or something to achieve this?
Use a pseudo element of the footer with border-radius to make the arch.
I made them different colors here so you can see which element is which.
body {
margin: 0;
max-height: 100vh;
overflow: hidden;
}
footer {
bottom: 0; left: 0; right: 0;
position: absolute;
background: brown;
height: 10vh;
}
footer::before {
content: '';
background: red;
width: 200%;
position: absolute;
left: 50%;
top: -100%;
transform: translateX(-50%);
height: 1000%;
border-radius: 50%;
z-index: -1;
}
<footer></footer>
This solution uses a large width to get a more pleasant curve, but without the pseudo-element:
footer {
background-color: red;
width: 200%;
transform: translateX(-25%);
height: 200px;
border-radius: 50% 50% 0 0;
}
<div>
<footer></footer>
</div>
Its not perfect, but here i've got a really really big circle that's absolutely positioned with the overflow hidden so that you only see the top part of the arc.
#container{
background: grey;
height:300px;
width:500px;
position:relative;
overflow:hidden;
}
#arc{
position: absolute;
top:200px;
left:-800px;
width:2000px;
height:2000px;
border-radius:2000px;
background:brown;
}
<div id="container">
<div id="arc">
</div>
</div>
https://jsfiddle.net/z9pq1026/
You can actually use border-radius to do this without a pseudo element.
.arc {
width: 100%;
height:500px;
background: #000000;
border-radius: 50% / 30px;
border-bottom-right-radius: 0;
border-bottom-left-radius: 0;
}
<div class="arc"></div>
will work just fine. Make sure that when you use:
border-radius: 50% / 30px;
the first property is always "50%" as this will ensure the arc meets in the middle. The second property (after the "/") is the height of the arc measured from the middle to the edges
The circle solution, but it's responsive!
footer {
background: #ececec;
height: 200px;
width: 100%;
position: relative;
overflow: hidden;
}
.arc {
position: absolute;
top: 0px;
right: calc(-80%);
width: 300%;
padding-top: 100%;
border-radius: 100%;
background: black;
}
<footer>
<div class="arc">
</div>
</footer>
I want to place a div (with position:absolute;) element in the center of the window. But I'm having problems doing so, because the width is unknown.
I tried the following CSS code, but it needs to be adjusted because the width is responsive.
.center {
left: 50%;
bottom: 5px;
}
How can I achieve this?
This works for me:
#content {
position: absolute;
left: 0;
right: 0;
margin-left: auto;
margin-right: auto;
width: 100px; /* Need a specific value to work */
}
<body>
<div>
<div id="content">
I'm the content
</div>
</div>
</body>
<body>
<div style="position: absolute; left: 50%;">
<div style="position: relative; left: -50%; border: dotted red 1px;">
I am some centered shrink-to-fit content! <br />
tum te tum
</div>
</div>
</body>
Responsive Solution
Here is a good solution for responsive design or unknown dimensions in general if you don't need to support IE8 and lower.
.centered-axis-x {
position: absolute;
left: 50%;
transform: translate(-50%, 0);
}
.outer {
position: relative; /* or absolute */
/* unnecessary styling properties */
margin: 5%;
width: 80%;
height: 500px;
border: 1px solid red;
}
.inner {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
/* unnecessary styling properties */
max-width: 50%;
text-align: center;
border: 1px solid blue;
}
<div class="outer">
<div class="inner">I'm always centered<br/>doesn't matter how much text, height or width i have.<br/>The dimensions or my parent are irrelevant as well</div>
</div>
Here is a JS Fiddle
The clue is, that left: 50% is relative to the parent while the translate transform is relative to the elements width/height.
This way you have a perfectly centered element, with a flexible width on both child and parent. Bonus: this works even if the child is bigger than the parent.
You can also center it vertically with this (and again, width and height of parent and child can be totally flexible (and/or unknown)):
.centered-axis-xy {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%,-50%);
}
Keep in mind that you might need transform vendor prefixed as well. For example -webkit-transform: translate(-50%,-50%);
<div style='position:absolute; left:50%; top:50%; transform: translate(-50%, -50%)'>
This text is centered.
</div>
This will center all the objects inside div with position type static or relative.
I just wanted to add if someone wants to do it with a single div tag then here is the way out:
Taking width as 900px.
#styleName {
position: absolute;
left: 50%;
width: 900px;
margin-left: -450px;
}
In this case one should know the width beforehand.
Responsive solution
Assuming the element in the div, is another div...
This solution works fine:
<div class="container">
<div class="center"></div>
</div>
The container can be any size (must be position relative):
.container {
position: relative; /* Important */
width: 200px; /* Any width */
height: 200px; /* Any height */
background: red;
}
The element (div) can also be any size (must be smaller than the container):
.center {
position: absolute; /* Important */
top: 50%; /* Position Y halfway in */
left: 50%; /* Position X halfway in */
transform: translate(-50%,-50%); /* Move it halfway back(x,y) */
width: 100px; /* Any width */
height: 100px; /* Any height */
background: blue;
}
The result will look like this. Run the code snippet:
.container {
position: relative;
width: 200px;
height: 200px;
background: red;
}
.center {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
width: 100px;
height: 100px;
background: blue;
}
<div class="container">
<div class="center"></div>
</div>
I found it very helpful.
Absolute Centre
HTML:
<div class="parent">
<div class="child">
<!-- content -->
</div>
</div>
CSS:
.parent {
position: relative;
}
.child {
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
Demo:
http://jsbin.com/rexuk/2/
It was tested in Google Chrome, Firefox, and Internet Explorer 8.
This works for vertical and horizontal:
#myContent{
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
}
And if you want make an element center of the parent, set the position of the parent relative:
#parentElement{
position: relative
}
For vertical center align, set the height to your element. Thanks to Raul.
If you want make an element center of the parent, set the position of the parent to relative
If you need to center horizontally and vertically too:
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
Searching for a solution, I got the previous answers and could make content centered with Matthias Weiler's answer, but using text-align:
#content{
position: absolute;
left: 0;
right: 0;
text-align: center;
}
It worked with Google Chrome and Firefox.
I understand this question already has a few answers, but I've never found a solution that would work in almost all classes that also makes sense and is elegant, so here's my take after tweaking a bunch:
.container {
position: relative;
}
.container .cat-link {
position: absolute;
left: 50%;
top: 50%;
transform: translate3d(-50%,-50%,0);
z-index: 100;
text-transform: uppercase; /* Forces CSS to treat this as text, not a texture, so no more blurry bugs */
background-color: white;
}
.color-block {
height: 250px;
width: 100%;
background-color: green;
}
<div class="container">
<a class="cat-link" href="">Category</a>
<div class="color-block"></div>
</div>
It is saying give me a top: 50% and a left: 50%, then transform (create space) on both the X/Y axis to the -50% value, in a sense "create a mirror space".
As such, this creates an equal space on all the four points of a div, which is always a box (has four sides).
This will:
Work without having to know the parent's height / width.
Work on responsive.
Work on either X or Y axis. Or both, as in my example.
I can't come up with a situation where it doesn't work.
Flexbox can be used to center an absolute positioned div.
display: flex;
align-items: center;
justify-content: center;
.relative {
width: 275px;
height: 200px;
background: royalblue;
color: white;
margin: auto;
position: relative;
}
.absolute-block {
position: absolute;
height: 36px;
background: orange;
padding: 0px 10px;
bottom: -5%;
border: 1px solid black;
}
.center-text {
display: flex;
justify-content: center;
align-items: center;
box-shadow: 1px 2px 10px 2px rgba(0, 0, 0, 0.3);
}
<div class="relative center-text">
Relative Block
<div class="absolute-block center-text">Absolute Block</div>
</div>
This is a mix of other answers, which worked for us:
.el {
position: absolute;
top: 50%;
margin: auto;
transform: translate(-50%, -50%);
}
This works on any random unknown width of the absolute positioned element you want to have in the centre of your container element:
Demo
<div class="container">
<div class="box">
<img src="https://picsum.photos/200/300/?random" alt="">
</div>
</div>
.container {
position: relative;
width: 100%;
}
.box {
position: absolute;
top: 0;
left: 0;
right: 0;
bottom: 0;
display: flex;
justify-content: center;
align-items: center;
}
It's possible to center an element that has aspect-ratio:1 with position absolute by using calc()
In the following example I'm using a circle because it's easier to explain and understand, but the same concept can be applied to any shape with aspect-ratio:1 meaning that the width and height are equal. (about aspect-ratio)
:root{
--diameter: 80px;
}
div{
position:absolute;
top: calc(50% - var(--diameter)/2);
right:calc(50% - var(--diameter)/2);
aspect-ratio:1;
width:var(--diameter);
border-radius:100%;
background:blue;
}
<div/>
Explanation
As far as I know, this is impossible to achieve for an unknown width.
You could - if that works in your scenario - absolutely position an invisible element with 100% width and height, and have the element centered in there using margin: auto and possibly vertical-align. Otherwise, you'll need JavaScript to do that.
I'd like to add on to bobince's answer:
<body>
<div style="position: absolute; left: 50%;">
<div style="position: relative; left: -50%; border: dotted red 1px;">
I am some centered shrink-to-fit content! <br />
tum te tum
</div>
</div>
</body>
Improved: /// This makes the horizontal scrollbar not appear with large elements in the centered div.
<body>
<div style="width:100%; position: absolute; overflow:hidden;">
<div style="position:fixed; left: 50%;">
<div style="position: relative; left: -50%; border: dotted red 1px;">
I am some centered shrink-to-fit content! <br />
tum te tum
</div>
</div>
</div>
</body>
Just wrap your content with a new div and use display flex and then use align-items: center; and justify-content: center; take a look...
<div class="firstPageContainer">
<div class="firstPageContainer__center"></div>
</div>
.firstPageContainer{
display: flex;
width: 1000px;
height: 1000px;
justify-content: center;
align-items: center;
background-color: #FF8527;
}
.firstPageContainer__center{
position:absolute;
width: 50px;
height: 50px;
background-color: #3A4147;
}
Sass/Compass version of a previous responsive solution:
#content {
position: absolute;
left: 50%;
top: 50%;
#include vendor(transform, translate(-50%, -50%));
}
This worked for me:
<div class="container><p>My text</p></div>
.container{
position: absolute;
left: 0;
right: 0;
margin-left: auto;
margin-right: auto;
}
My preferred centering method:
position: absolute;
margin: auto;
width: x%
absolute block element positioning
margin auto
same left/right, top/bottom
A JSFiddle is here.
Here's a useful jQuery plugin to do this. I found it here. I don't think it's possible purely with CSS.
/**
* #author: Suissa
* #name: Absolute Center
* #date: 2007-10-09
*/
jQuery.fn.center = function() {
return this.each(function(){
var el = $(this);
var h = el.height();
var w = el.width();
var w_box = $(window).width();
var h_box = $(window).height();
var w_total = (w_box - w)/2; //400
var h_total = (h_box - h)/2;
var css = {"position": 'absolute', "left": w_total + "px", "top":
h_total + "px"};
el.css(css)
});
};
#container
{
position: relative;
width: 100%;
float: left
}
#container .item
{
width: 50%;
position: absolute;
margin: auto;
left: 0;
right: 0;
}
HTML:
<div id='parent'>
<div id='child'></div>
</div>
CSS:
#parent {
display: table;
}
#child {
display: table-cell;
vertical-align: middle;
}
I know I already provided an answer, and my previous answer, along with others given, work just fine. But I have used this in the past and it works better on certain browsers and in certain situations. So I thought I'd give this answer as well. I did not "Edit" my previous answer and add it because I feel this is an entirely separate answer and the two I have provided are not related.
The accepted solution of this question didn't work for my case...
I'm doing a caption for some images and I solved it using this:
top: 0;
left: 0;
right: 0;
margin-left: auto;
margin-right: auto;
display: flex;
align-items: center;
figure {
position: relative;
width: 325px;
display: block
}
figcaption{
position: absolute;
background: #FFF;
width: 120px;
padding: 20px;
-webkit-box-shadow: 0 0 30px grey;
box-shadow: 0 0 30px grey;
border-radius: 3px;
display: block;
top: 0;
left: 0;
right: 0;
margin-left: auto;
margin-right: auto;
display: flex;
align-items: center;
}
<figure>
<img src="https://picsum.photos/325/600">
<figcaption>
But as much
</figcaption>
</figure>
HTML
<div id='parent'>
<div id='centered-child'></div>
</div>
CSS
#parent {
position: relative;
}
#centered-child {
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto auto;
}
http://jsfiddle.net/f51rptfy/
This solution works if the element has width and height
.wrapper {
width: 300px;
height: 200px;
background-color: tomato;
position: relative;
}
.content {
width: 100px;
height: 100px;
background-color: deepskyblue;
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
<div class="wrapper">
<div class="content"></div>
</div>
.center {
position: absolute
left: 50%;
bottom: 5px;
}
.center:before {
content: '';
display: inline-block;
margin-left: -50%;
}
This is a trick I figured out for getting a DIV to float exactly in the center of a page. It is really ugly of course, but it works in all browsers.
Dots and Dashes
<div style="border: 5 dashed red;position:fixed;top:0;bottom:0;left:0;right:0;padding:5">
<table style="position:fixed;" width="100%" height="100%">
<tr>
<td style="width:50%"></td>
<td style="text-align:center">
<div style="width:200;border: 5 dashed green;padding:10">
Perfectly Centered Content
</div>
</td>
<td style="width:50%"></td>
</tr>
</table>
</div>
Cleaner
Wow, those five years just flew by, didn't they?
<div style="position:fixed;top:0px;bottom:0px;left:0px;right:0px;padding:5px">
<table style="position:fixed" width="100%" height="100%">
<tr>
<td style="width:50%"></td>
<td style="text-align:center">
<div style="padding:10px">
<img src="Happy.PM.png">
<h2>Stays in the Middle</h2>
</div>
</td>
<td style="width:50%"></td>
</tr>
</table>
</div>
HTML:
<div class="wrapper">
<div class="inner">
content
</div>
</div>
CSS:
.wrapper {
position: relative;
width: 200px;
height: 200px;
background: #ddd;
}
.inner {
position: absolute;
top: 0; bottom: 0;
left: 0; right: 0;
margin: auto;
width: 100px;
height: 100px;
background: #ccc;
}
This and more examples here.