背景 | background (Backgrounds & Borders) - CSS 中文开发手册 - Break易站
背景 | background (Backgrounds & Borders) - CSS 中文开发手册
CSS background速记属性允许您一次调整所有可用的背景样式选项,包括彩色图像,原点和大小,重复方法以及其他功能。background可用于对一个或多个设置值:background-clip,background-color,background-image,background-origin,background-position,background-repeat,background-size,和background-attachment。
/* 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");
backgroundCSS简写属性明确分配给定的值,并设置缺少的属性为初始值。
初始值 | 作为简写的每个属性:background-image:none background-position:0%0%background-size:auto auto background-repeat:repeat background-origin:padding-box background-clip:border-box background-attachment :滚动背景颜色:透明 |
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适用于 | 所有元素。它也适用于:: first-letter和:: first-line。 |
遗传 | 没有 |
百分比 | 作为简写的每个属性:background-position:指背景定位区域的大小减去背景图像的大小; 大小是指水平偏移的宽度和垂直偏移的高度background-size:相对于背景定位区域 |
媒体 | 视觉 |
计算值 | 作为速记的每个属性:background-image:如指定的那样,但url值被设置为absolute-background-position:一个列表,每个项目由两个关键字组成,这两个关键字分别代表原点和来自该原点的两个偏移量,每个偏移量都以绝对值长度(如果给定<length>),否则为百分比background-size:按照指定,但相对长度转换为绝对长度background-repeat:列表,每个项目由两个关键字组成,每个维度一个background-origin:如指定background-clip:指定background-attachment:指定background-color:计算颜色 |
动画类型 | 作为简写的每个属性:background-color:一种颜色background-image:离散background-clip:离散background-position:长度,百分比或calc的简单列表的可重复列表background-size:简单列表的可重复列表长度,百分比或计算背景重复:离散背景附件:离散 |
规范的顺序 | 出现在价值形式语法中的顺序 |
background-image: none background-position: 0% 0% background-size: auto auto background-repeat: repeat background-origin: padding-box background-clip: border-box background-attachment: scroll background-color: transparent
Applies to all elements. It also applies to [`::first-letter`](::first-letter) and [`::first-line`](::first-line). [Inherited](inheritance) no Percentages as each of the properties of the shorthand:
background-position:指背景定位区域的大小减去背景图像的大小; 大小是指水平偏移的宽度和垂直偏移的高度background-size:相对于背景定位区域
Media visual [Computed value](computed_value) as each of the properties of the shorthand:
background-image:如指定的那样,但是具有url绝对值background-position:一个列表,每个项目由两个关键字组成,代表原点和来自该原点的两个偏移量,每个以绝对长度给出(如果给定 <length>),否则以百分比background-size:按照规定,但相对长度转换为绝对长度background-repeat:一个列表,每个项目由两个关键字组成,每个维度一个background-origin: 作为指定background-clip: 作为指定background-attachment: 作为指定background-color:计算颜色
Animation type as each of the properties of the shorthand:
background-color:一种颜色 background-image:离散background-clip:离散background-position:长度,百分比或计算的简单列表的可重复列表background-size:长度,百分比或计算的简单列表的可重复列表background-repeat:离散background-attachment:离散
Canonical order order of appearance in the formal grammar of the values
句法
background属性被指定为一个或多个背景层,用逗号分隔。
每个图层的语法如下所示:
每个图层可能包含零个或一个以下任何值: <attachment><bg-image><position><bg-size><repeat-style><bg-size>值可能仅在紧跟在<position>“/”字符之后,如下所示:“ center/80%”。<box>值可能包含零次,一次或两次。如果包含一次,它会同时设置background-origin和background-clip。如果它包含两次,第一次出现background-origin,第二次background-clip。<background-color>值可能只包含在指定的最后一个图层中。
值
<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。
形式语法
[ <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-boxwhere <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>?
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: pink; } .topbanner { background: url("https://mdn.mozillademos.org/files/11983/starsolid.gif") #99f repeat-y fixed; }
结果
规范
规范 | 状态 | 评论 |
---|---|---|
CSS背景和边框模块级别3在该规范中定义“背景”。 | 候选推荐 | 速记属性已扩展为支持多个背景和新的背景大小,背景源和背景剪辑属性。 |
CSS级别2(修订1)该规范中“背景”的定义。 | 建议 | 没有重大变化 |
CSS级别1该规范中“背景”的定义。 | 建议 | 初始定义 |
浏览器兼容性
特征 | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
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基本支持 | 1.0 | 12 | 1.0 | 4 | 3.5 | 1.0 |
多个背景 | 1.0 | 12 | 3.6 | 9 | 10.5 | 1.3 |
SVG图像作为背景 | 31.0 | 12 | 9.0 | 9.0 | 21.0 | 5.1 |
背景尺寸longhand的值 | 21.0 | 12 | 9.0 | 9.0 | 21.0 | 5.1 |
背景来源的longhand值 | 21.0 | 12 | 22.0 | 9.0 | 21.0 | 5.1 |
背景剪辑longhand的值 | 21.0 | 12 | 22.0 | 9.0 | 21.0 | 5.1 |
特征 | Android | Chrome for Android | Edge mbile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
基本支持 | 2.1 | ? | (是) | 1.0 | 10.0 | 5.0 | 3.2 |
多个背景 | 2.1 | ? | (是) | 1.0 | 10.0 | ? | 3.2 |
SVG图像作为背景 | 3.0 | ? | (是) | 4.0 | 10.0 | (是) | 4.2 |
背景尺寸longhand的值 | 3.0 | ? | (是) | 18.0 | 10.0 | (是) | 4.0 |
背景来源的longhand值 | 3.0 | ? | (是) | 22.0 | 10.0 | 没有 | 4.0 |
背景剪辑longhand的值 | 3.0 | ? | (是) | 22.0 | 10.0 | 没有 | 4.0 |