repeating-radial-gradient()

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CSS函数repeating-radial-gradient() 创建一个从原点辐射的重复渐变组成的<image> 。它类似于radial-gradient 并且采用相同的参数,但是它会在所有方向上重复颜色,以覆盖其整个容器。函数的结果是  <gradient> 数据类型的对象, 是一种特殊的<image>类型。

/* 一个从容器中心点开始的重复渐变,
   从红色开始,渐变到蓝色,再渐变到绿色 */
repeating-radial-gradient(circle at center, red 0, blue, green 30px);

With each repetition, the positions of the color stops are shifted by a multiple of the dimensions of the basic radial gradient (the distance between the last color stop and the first). Thus, the position of each ending color stop coincides with a starting color stop; if the color values are different, this will result in a sharp visual transition.

As with any gradient, a repeating radial gradient has no intrinsic dimensions; i.e., it has no natural or preferred size, nor a preferred ratio. Its concrete size will match the size of the element it applies to.

Usage note: Because <gradient>s belong to the <image> data type, they can only be used where <image>s can be used. For this reason, repeating-radial-gradient() won't work on background-color and other properties that use the <color> data type.

Syntax

Values

<position>
The position of the gradient, interpreted in the same way as background-position or transform-origin. If unspecified, it defaults to center.
<angle>
The angle of the gradient line, which extends from the starting point at this angle. If unspecified, it defaults to 0deg.
<shape>
The gradient's shape. The value can be circle (meaning that the gradient's shape is a circle with constant radius) or ellipse (meaning that the shape is an axis-aligned ellipse). If unspecified, it defaults to ellipse.
<extent-keyword>
A keyword describing how big the ending shape must be. The possible values are:
Keyword Description
closest-side The gradient's ending shape meets the side of the box closest to its center (for circles) or meets both the vertical and horizontal sides closest to the center (for ellipses).
closest-corner The gradient's ending shape is sized so that it exactly meets the closest corner of the box from its center.
farthest-side Similar to closest-side, except the ending shape is sized to meet the side of the box farthest from its center (or vertical and horizontal sides).
farthest-corner The gradient's ending shape is sized so that it exactly meets the farthest corner of the box from its center.

Note: Early implementations of this function included other keywords (cover and contain) as synonyms of the standard farthest-corner and closest-side, respectively. Use the standard keywords only, as some implementations have already dropped those older variants.

<color-stop>
A color-stop's <color> value, followed by an optional stop position (either a <percentage> or a <length> along the gradient's axis). A percentage of 0%, or a length of 0, represents the center of the gradient; the value 100% represents the intersection of the ending shape with the virtual gradient ray. Percentage values in between are linearly positioned on the gradient ray.

Formal syntax

repeating-radial-gradient( 
       [[ circle  || <length> ]                     [at <position>]? , | 
        [ ellipse || [<length> | <percentage> ]{2}] [at <position>]? , |
        [[ circle | ellipse ] || <extent-keyword> ] [at <position>]? , |
                                                     at <position>   ,    <color-stop> [ , <color-stop> ]+ )
        \---------------------------------------------------------------/\--------------------------------/
                  Contour, size and position of the ending shape               List of color stops  
    
where <extent-keyword> = closest-corner | closest-side | farthest-corner | farthest-side
  and <color-stop> = <color> [ <percentage> | <length> ]?

Examples

Radial gradients run along an axis. At each end point of the axis, a radius is specified. This can be imagined as creating two "circles", where for each circle the center is specified by the point and the radius is specified by the radius length. The gradient runs outwards from the circumference of the inner circle to the circumference of the outer circle.

Black and white gradient

background: repeating-radial-gradient(black, black 5px, white 5px, white 10px);

Farthest-corner

background: repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);

Specifications

Specification Status Comment
CSS Images Module Level 3
repeating-radial-gradient()
Candidate Recommendation Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (on background and background-image) 10 -webkit 3.6 (1.9.2)-moz
16 (16)[1]
10 12 -o
12.5
5.1 -webkit
On border-image (Yes) 29 (29) (Yes) (Yes) (Yes)
On any other property that accept <image> 未实现 (Yes) (Yes) (Yes) (Yes)
Interpolation hints (a percent without a color) 40 36 (36) ? ? ?
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support (on background and background-image) 4.4 46.0 (46) 10 12.1 7.1
On border-image 29.0 (29) (Yes) (Yes) (Yes) (Yes)
On any other property that accept <image> 未实现 (Yes) (Yes) (Yes) (Yes)

[1] Before Firefox 36, Gecko didn't apply gradient on the pre-multiplied color space, leading to shade of grey unexpectedly appearing when used with transparency. Since Firefox 42, the prefixed version of gradients can be disabled by setting layout.css.prefixes.gradients to false.

In addition to the unprefixed support, Gecko 44.0 (Firefox 44.0 / Thunderbird 44.0 / SeaMonkey 2.41) added support for a -webkit prefixed version of the function for web compatibility reasons behind the preference layout.css.prefixes.webkit, defaulting to false. Since Gecko 49.0 (Firefox 49.0 / Thunderbird 49.0 / SeaMonkey 2.46) the preference defaults to true.

See also

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