7 ways to achieve centering with CSS_html/css_WEB-ITnose-HTML Tutorial-php.cn

Implementing the centering of HTML elements seems simple, but in fact it is not.

Horizontal centering is easy, vertical centering is more difficult, and horizontal and vertical centering is even more difficult. In this era of responsive layout, it is difficult to fix the width and height of elements. I have counted several current methods. This article introduces each step from the shallower to the deeper, using the same HTML code:

<div class="center">

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<img src="jimmy-choo-shoe.jpg" alt="">

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</div>

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The shoe image below will change but the original size is always 500px × 500px, and the theme background color is used HSL colors

1. Center horizontally? Use text-align

In some scenarios the simple method is the best method

div.center { text-align: center; background: hsl(0, 100%, 97%); }

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div.center img { width: 33%; height: auto; }

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But this method cannot center the image vertically: you need to add padding to the div or add margin-top and margin-bottom to the elements in the div

2. margin: auto center

is also horizontally centered, with the same limitations as the first method:

div.center { background: hsl(60, 100%, 97%); }

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div.center img { display: block; width: 33%; height: auto; margin: 0 auto; }

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Note that display: block, in this case there must be margin: 0 auto.

3. table-cell centered

Using display: table-cell, you can achieve horizontal and vertical centering. Often it is necessary to add an additional empty element.

<div class="center-aligned">

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<div class="center-core">

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<img src="jimmy-choo-shoe.jpg">

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</div>

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</div>

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CSS code:

.center-aligned { display: table; background: hsl(120, 100%, 97%);width: 100%; }

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.center-core { display: table-cell; text-align: center; vertical-align:middle; }

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.center-core img { width: 33%; height: auto; }

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Note that width: 100% is to prevent the div from collapsing, and the outer container needs a height to be vertically centered. If the vertically centered element is placed in . body, you need to set height for html and body. Valid in all browsers, including IE8.

4. Absolute centering

A new technology recently promoted by Stephen Shaw can be well compatible with various browsers. The only drawback is that the outer container must declare height

.absolute-aligned {

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position: relative; min-height: 500px;

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background: hsl(200, 100%, 97%);

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.absolute-aligned img {

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width: 50%;

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min-width: 200px;

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height: auto;

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overflow: auto; margin: auto;

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position: absolute;

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top: 0; left: 0; bottom: 0; right: 0;

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Stephen verified many versions of this code in his article

5. Use translate to center

Chris Coiyer proposed a new method: using CSS transforms . Supports both horizontal and vertical centering:

.center { background: hsl(180, 100%, 97%); position: relative; min-height: 500px; }

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.center img { position: absolute; top: 50%; left: 50%;

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transform: translate(-50%, -50%); width: 30%; height: auto; }

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has the following disadvantages:

CSS transform needs to be used specifically for different browsers The prefix (-moz or -o or -webkit)

is not valid in lower versions of IE (IE8 and below)

The external container needs to set the height (or gain it in some other way ) Because it cannot get the height from its absolutely-positioned content.

If the content contains text, the current browser composition technology interprets the text very vaguely.

6. Use Flexbox to center

This approach will likely become the preferred centering solution once attribute variables and specific prefixes disappear.

.center { background: hsl(240, 100%, 97%); display: flex; justify-content: center; align-items: center; }

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.center img { width: 30%; height: auto; }

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in In many ways flexbox is the simplest solution, but the constraints are various archaic syntax and lower versions of IE (although display: table-cell is an acceptable solution). Full CSS code:

.center { background: hsl(240, 100%, 97%);

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display: -webkit-box; /* OLD: Safari, iOS 6 and earlier; Android browser, older WebKit */

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display: -moz-box; /* OLD: Firefox (can be buggy) */

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display: -ms-flexbox; /* OLD: IE 10 */

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display: -webkit-flex; /* FINAL, PREFIXED, Chrome 21+ */

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display: flex; /* FINAL: Opera 12.1+, Firefox 22+ */

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-webkit-box-align: center;

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-moz-box-align: center;

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-ms-flex-align: center;

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-webkit-align-items: center;

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align-items: center;

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-webkit-box-pack: center;

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-moz-box-pack: center;

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-ms-flex-pack: center;

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-webkit-justify-content: center;

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justify-content: center;

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Now that the specification has been formed and browsers support it, I have written extensively on flexbox layout and its uses.

7. Use calc to center

In a More versatile than flexbox in some scenarios:

.center { background: hsl(300, 100%, 97%); min-height: 600px; position:relative; }

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.center img { width: 40%; height: auto; position: absolute; top:calc(50% - 20%); left: calc(50% - 20%); }

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Obviously, calc allows calculations to be performed on the current page layout. In the above example, 50% is the midpoint of the element in the container, but used alone would make the upper left corner of the image in the middle of the

. We need to pull the width and height back a little, so that the sizes are half of the width and height of the image respectively. The expression is as follows:

top: calc(50% - (40% / 2)); left: calc(50% - (40% / 2));

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In current browsers, you can find that this technology works best when the content is fixed and the size is known:

.center img { width: 500px; height: 500px; position: absolute; top:calc(50% - (300px / 2)); left: calc(50% - (300px ? 2)); }

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calc This method also has many potential shortcomings like flexbox: it supports Firefox 4 and higher browsers. For earlier browsers, you need to add a prefix, and IE8 is not supported. The complete code for image centering:

.center img { width: 40%; height: auto; position: absolute;

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top: -webkit-calc(50% - 20%); left: -webkit-calc(50% - 20%);

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top: -moz-calc(50% - 20%); left: -moz-calc(50% - 20%);

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top: calc(50% - 20%); left: calc(50% - 20%); }

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Of course there are many other methods, such as using pseudo elements to vertically center, understanding these techniques can Let web developers deal with centering issues without getting stuck!

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CSS实现居中的7种方法

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