background

摘要

background 是CSS简写属性，用来集中设置各种背景属性。background 可以用来设置一个或多个属性:background-color, background-image, background-position, background-repeat, background-size, background-attachment。

background 将指定的背景属性设为明确给定的值，将没有指定的背景属性设为初始值。

语法

/* Using a <background-color> */
background: green;
/* Using a <bg-image> and <repeat-style> */
background: url("test.jpg") repeat-y;
/* Using a <box> and <background-color> */
background: border-box red;
/* A single image, centered and scaled */
background: no-repeat center/80% url("../img/image.png");

值

下面的一个或多个值，可以按任意顺序放置：

<attachment>

参看 background-attachment

<box>

参看 background-clip

<background-color>

参看 background-color

<bg-image>

参看 background-image

<position>

See background-position

<repeat-style>

参看 background-repeat

<bg-size>

参看 background-size. 这个属性的定义必须在 <position> 之后, 并使用 '/' 符号分隔。

标准语法 

[ <bg-layer> , ]* <final-bg-layer>
where 
<bg-layer> = <bg-image> || <position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2}
<final-bg-layer> = <bg-image> || <position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box> || <box> || <'background-color'>
where 
<bg-image> = none | <image>
<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>
<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} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <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}
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>
<color-stop> = <color> <length-percentage>?

实例

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") #00D repeat-y fixed;
}

结果

规范

浏览器兼容

• Desktop
• Mobile

其他参考

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