background

尝试一下

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。

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。

注意： background-color 只能在 background 的最后一个属性上定义，因为整个元素只有一种背景颜色。

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

background = 
  [ <bg-layer># , ]? <final-bg-layer>  

<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>                           

<bg-image> = 
  <image>  |
  none     

<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 [0,∞]> | 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  

<image> = 
  <url>           |
  <image()>       |
  <image-set()>   |
  <cross-fade()>  |
  <element()>     |
  <gradient>      

<length-percentage> = 
  <length>      |
  <percentage>  

<image()> = 
  image( <image-tags>? [ <image-src>? , <color>? ]! )  

<image-set()> = 
  image-set( <image-set-option># )  

<cross-fade()> = 
  cross-fade( <cf-image># )  

<element()> = 
  element( <id-selector> )  

<gradient> = 
  <linear-gradient()>            |
  <repeating-linear-gradient()> (en-US)  |
  <radial-gradient()>            |
  <repeating-radial-gradient()> (en-US)  

<image-tags> = 
  ltr  |
  rtl  

<image-src> = 
  <url>     |
  <string>  

<color> = 
  <absolute-color-base>  |
  currentcolor           |
  <system-color>         |
  <device-cmyk()>        

<image-set-option> = 
  [ <image> | <string> ] [ <resolution> || type( <string> ) ]  

<cf-image> = 
  <percentage>?          &&
  [ <image> | <color> ]  

<id-selector> = 
  <hash-token>  

<linear-gradient()> = 
  linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )  

<radial-gradient()> = 
  radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )  

<absolute-color-base> = 
  <hex-color> (en-US)    |
  <named-color>  |
  transparent    |
  <rgb()>        |
  <rgba()>       |
  <hsl()>        |
  <hsla()>       |
  <hwb()>        |
  <lab()>        |
  <lch()>        |
  <oklab()>      |
  <oklch()>      |
  <color()>      

<device-cmyk()> = 
  device-cmyk( <cmyk-component>{4} [ / <alpha-value> ]? )  

<side-or-corner> = 
  [ left | right ]  ||
  [ top | bottom ]  

<color-stop-list> = 
  <linear-color-stop> , [ <linear-color-hint>? , <linear-color-stop> ]#  

<position> = 
  [ left | center | right | top | bottom | start | end | <length-percentage> ]  |
  [ left | center | right | x-start | x-end | <length-percentage> ] [ top | center | bottom | y-start | y-end | <length-percentage> ]  |
  [ center | [ left | right | x-start | x-end ] <length-percentage>? ] && [ center | [ top | bottom | y-start | y-end ] <length-percentage>? ]  |
  [ center | [ start | end ] <length-percentage>? ] [ center | [ start | end ] <length-percentage>? ]  

<rgb()> = 
  rgb( [ <percentage> | none ]{3} [ / [ <alpha-value> | none ] ]? )  |
  rgb( [ <number> | none ]{3} [ / [ <alpha-value> | none ] ]? )  

<hsl()> = 
  hsl( [ <hue> | none ] [ <percentage> | none ] [ <percentage> | none ] [ / [ <alpha-value> | none ] ]? )  

<hwb()> = 
  hwb( [ <hue> | none ] [ <percentage> | none ] [ <percentage> | none ] [ / [ <alpha-value> | none ] ]? )  

<lab()> = 
  lab( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ / [ <alpha-value> | none ] ]? )  

<lch()> = 
  lch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )  

<oklab()> = 
  oklab( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ / [ <alpha-value> | none ] ]? )  

<oklch()> = 
  oklch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )  

<color()> = 
  color( <colorspace-params> [ / [ <alpha-value> | none ] ]? )  

<cmyk-component> = 
  <number>      |
  <percentage>  

<alpha-value> = 
  <number>      |
  <percentage>  

<linear-color-stop> = 
  <color>               &&
  <length-percentage>?  

<linear-color-hint> = 
  <length-percentage>  

<hue> = 
  <number>  |
  <angle>   |
  none      

<colorspace-params> = 
  <predefined-rgb-params>  |
  <xyz-params>             

<predefined-rgb-params> = 
  <predefined-rgb> [ <number> | <percentage> | none ]{3}  

<xyz-params> = 
  <xyz-space> [ <number> | none ]{3}  

<predefined-rgb> = 
  srgb          |
  srgb-linear   |
  display-p3    |
  a98-rgb       |
  prophoto-rgb  |
  rec2020       

<xyz-space> = 
  xyz      |
  xyz-d50  |
  xyz-d65

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

规范	状态	注释
CSS Backgrounds and Borders Module Level 3 background	Candidate Recommendation	此简写属性已经扩展出了多重背景和诸如 `background-size`，`background-origin` 与 `background-clip` 等新属性。
CSS Level 2 (Revision 1) background	Recommendation	无重大修改
CSS Level 1 background	Recommendation	初始定义

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