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CSS-背景重复 | background-repeat

日期：2018-09-12点击：627收藏

ground-repeatCSS 属性定义背景图像的重复方式。背景图像可以沿着水平轴，垂直轴，两个轴重复，或者根本不重复。

/* One-value syntax */
background-repeat: repeat-x;
background-repeat: repeat-y;
background-repeat: repeat;
background-repeat: space;
background-repeat: round;
background-repeat: no-repeat;

/* Two-value syntax: horizontal | vertical */
background-repeat: repeat space;
background-repeat: repeat repeat;
background-repeat: round space;
background-repeat: no-repeat round;

/* Global values */
background-repeat: inherit;
background-repeat: initial;
background-repeat: unset;

默认情况下，重复的图像被裁剪为元素的大小，但可以缩放以适合（使用round）或者从头到尾均匀分布（使用space）。

初始值	repeat
适用元素	all elements. It also applies to ::first-letter and ::first-line.
是否是继承属性	no
适用媒体	visual
计算值	a list, each item consisting of two keywords, one per dimension
Animation type	discrete
正规顺序	the unique non-ambiguous order defined by the formal grammar

语法

值

<repeat-style>单值语法是完整的双值语法的缩写：

单值	等价于双值
repeat-x	repeat no-repeat
repeat-y	no-repeat repeat
repeat	repeat repeat
space	space space
round	round round
no-repeat	no-repeat no-repeat

在双值语法中, 第一个值表示水平重复行为, 第二个值表示垂直重复行为. 下面是关于每一个值是怎么工作的具体说明:

repeat	图像会按需重复来覆盖整个背景图片所在的区域. 最后一个图像会被裁剪, 如果它的大小不合适的话.
space	图像会尽可能得重复, 但是不会裁剪. 第一个和最后一个图像会被固定在元素(element)的相应的边上, 同时空白会均匀地分布在图像之间. `background-position`属性会被忽视, 除非只有一个图像能被无裁剪地显示. 只在一种情况下裁剪会发生, 那就是图像太大了以至于没有足够的空间来完整显示一个图像.
round	随着允许的空间在尺寸上的增长, 被重复的图像将会伸展(没有空隙), 直到有足够的空间来添加一个图像. 当下一个图像被添加后, 所有的当前的图像会被压缩来腾出空间. 例如, 一个图像原始大小是260px, 重复三次之后, 可能会被伸展到300px, 直到另一个图像被加进来. 这样他们就可能被压缩到225px.
no-repeat	图像不会被重复(因为背景图像所在的区域将可能没有完全被覆盖). 那个没有被重复的背景图像的位置是由`background-position`属性来决定.

正式语法

<repeat-style>#where 
<repeat-style> = repeat-x | repeat-y | [ repeat | space | round | no-repeat ]{1,2}

示例

HTML

<ol>
  <li>no-repeat
    <div class="one"></div>
  </li>
  <li>repeat
    <div class="two"></div>
  </li>
  <li>repeat-x
    <div class="three"></div>
  </li>
  <li>repeat-y
    <div class="four"></div>
  </li>
  <li>space
    <div class="five"></div>
  </li>
  <li>round
    <div class="six"></div>
  </li>
  <li>repeat-x, repeat-y (multiple images)
    <div class="seven"></div>
  </li>
</ol>

CSS

/* Shared for all DIVS in example */
ol,
li {
  margin: 0;
  padding: 0;
}
li {
  margin-bottom: 12px;
}
div {
    background-image: url(https://mdn.mozillademos.org/files/12005/starsolid.gif);
    width: 160px;
    height: 70px;
}

/* Background repeats */
.one {
  background-repeat: no-repeat;
}
.two {
  background-repeat: repeat;
}
.three {
  background-repeat: repeat-x;
}
.four {
  background-repeat: repeat-y;
}
.five {
  background-repeat: space;
}
.six {
  background-repeat: round;
}

/* Multiple images */
.seven {
  background-image:  url(https://mdn.mozillademos.org/files/12005/starsolid.gif),
                     url(https://developer.cdn.mozilla.net/media/redesign/img/favicon32.png);
  background-repeat: repeat-x,
                     repeat-y;
  height: 144px;
}

结果

在这个例子中, 每一个列表项都使用了不同的background-repeat语法.

规范

Specification	Status	Comment
CSS Backgrounds and Borders Module Level 3The definition of 'background-repeat' in that specification.	Candidate Recommendation	Adds support for multiple background images, the two-value syntax allowing distinct repetition behavior for the horizontal and vertical directions, the space and round keywords, and for backgrounds on inline-level elements by precisely defining the background painting area.
CSS Level 2 (Revision 1)The definition of 'background-repeat' in that specification.	Recommendation	No significant changes.
CSS Level 1The definition of 'background-repeat' in that specification.	Recommendation	Initial definition.

浏览器兼容性

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic Support	1.0	12	1.0	4	3.5	1.0
Multiple backgrounds	1.0	12	3.6	9	10.5	1.3
Two-value syntax (different values for x & y directions)	(Yes)	12	13.0	9.0	(Yes)	(Yes)
round and space keywords	(Yes)	12	49.0	9.0	10.5	(Yes)

Feature	Android	Chrome for Android	Edge mobile	Firefox for Android	IE mobile	Opera Android	iOS Safari
Basic Support	?	?	(Yes)	1.0	?	?	?
Multiple backgrounds	?	?	(Yes)	(Yes)	?	?	?
Two-value syntax (different values for x & y directions)	?	?	(Yes)	13.0	?	?	?
round and space keywords	?	?	(Yes)	49.0	?	?	?