background

background 是一种 CSS 简写属性，用于一次性集中定义各种背景属性，包括 color, image, origin 与 size, repeat 方式等等。

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

此属性是一个 简写属性，可以在一次声明中定义一个或多个属性：background-clip、background-color、background-image、background-origin、background-position、background-repeat、background-size，和 background-attachment。

对于所有简写属性，任何没有被指定的值都会被设定为它们的 初始值。

语法

/* 使用 <background-color> */
background: green;

/* 使用 <bg-image> 和 <repeat-style> */
background: url("test.jpg") repeat-y;

/* 使用 <box> 和 <background-color> */
background: border-box red;

/* 将背景设为一张居中放大的图片 */
background: no-repeat center/80% url("../img/image.png");

background 属性被指定多个背景层时，使用逗号分隔每个背景层。

每一层的语法如下：

• 在每一层中，下列的值可以出现 0 次或 1 次：
  • <attachment>
  • <bg-image>
  • <position>
  • <bg-size>
  • <repeat-style>
• <bg-size> 只能紧接着 <position> 出现，以"/"分割，如： "center/80%".
• <box> 可能出现 0 次、1 次或 2 次。如果出现 1 次，它同时设定 background-origin 和 background-clip。如果出现 2 次，第一次的出现设置 background-origin，第二次的出现设置 background-clip。
• <background-color> 只能被包含在最后一层。

值

下面的一个或多个值，可以按任意顺序放置：

<attachment>

参见 background-attachment

<box>

参见 background-clip 和 background-origin

<background-color>

参见 background-color

<bg-image>

参见 background-image

<position>

参见 background-position

<repeat-style>

参见 background-repeat

<bg-size>

参见 background-size。

标准语法

[ <bg-layer> , ]* <final-bg-layer>
where 
<bg-layer> = <bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box> || <box>
<final-bg-layer> = <'background-color'> || <bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box> || <box>
where 
<bg-image> = none | <image>
<bg-position> = [ [ left | center | right | top | bottom | <length-percentage> ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ] | [ center | [ left | right ] <length-percentage>? ] && [ center | [ top | bottom ] <length-percentage>? ] ]
<bg-size> = [ <length-percentage> | auto ]{1,2} | cover | contain
<repeat-style> = repeat-x | repeat-y | [ repeat | space | round | no-repeat ]{1,2}
<attachment> = scroll | fixed | local
<box> = border-box | padding-box | content-box
where 
<image> = <url> | <image()> | <image-set()> | <element()> | <cross-fade()> | <gradient>
<length-percentage> = <length> | <percentage>
where 
<image()> = image( [ [ <image> | <string> ]? , <color>? ]! )
<image-set()> = image-set( <image-set-option># )
<element()> = element( <id-selector> )
<cross-fade()> = cross-fade( <cf-mixing-image> , <cf-final-image>? )
<gradient> = <linear-gradient()> | <repeating-linear-gradient()> | <radial-gradient()> | <repeating-radial-gradient()>
where 
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
<image-set-option> = [ <image> | <string> ] <resolution>
<id-selector> = <hash-token>
<cf-mixing-image> = <percentage>? && <image>
<cf-final-image> = <image> | <color>
<linear-gradient()> = linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<repeating-linear-gradient()> = repeating-linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<radial-gradient()> = radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )
<repeating-radial-gradient()> = repeating-radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )
where 
<rgb()> = rgb( <percentage>{3} [ / <alpha-value> ]? ) | rgb( <number>{3} [ / <alpha-value> ]? ) | rgb( <percentage>#{3} , <alpha-value>? ) | rgb( <number>#{3} , <alpha-value>? )
<rgba()> = rgba( <percentage>{3} [ / <alpha-value> ]? ) | rgba( <number>{3} [ / <alpha-value> ]? ) | rgba( <percentage>#{3} , <alpha-value>? ) | rgba( <number>#{3} , <alpha-value>? )
<hsl()> = hsl( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsl( <hue>, <percentage>, <percentage>, <alpha-value>? )
<hsla()> = hsla( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsla( <hue>, <percentage>, <percentage>, <alpha-value>? )
<side-or-corner> = [ left | right ] || [ top | bottom ]
<color-stop-list> = <color-stop>#{2,}
<ending-shape> = circle | ellipse
<size> = closest-side | farthest-side | closest-corner | farthest-corner | <length> | <length-percentage>{2}
<position> = [ [ left | center | right ] || [ top | center | bottom ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]? | [ [ left | right ] <length-percentage> ] && [ [ top | bottom ] <length-percentage> ] ]
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>
<color-stop> = <color> <length-percentage>?

示例

HTML

<p class="topbanner">
  Starry sky<br/>
  Twinkle twinkle<br/>
  Starry sky
</p>
<p class="warning">Here is a paragraph<p>

CSS

.warning { 
  background: red; 
}

.topbanner { 
  background: url("https://mdn.mozillademos.org/files/11983/starsolid.gif") #99f repeat-y fixed; 
}

结果

规范

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

参见

• -moz-background-size, -moz-background-inline-policy
• 使用渐变背景
• 多重背景