径向梯度 | radial-gradient()

The radial-gradient() CSS function creates an <image> which represents a progressive transition between two or more colors radiating from an origin (the center of the gradient). Its shape may be a circle or an ellipse.

/* A gradient at the center of its container,
   starting red, changing to blue, and finishing green */
radial-gradient(circle at center, red 0, blue, green 100%)

As with any gradient, a 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.

To create a radial-gradient that repeats so as to fill its container, use the repeating-radial-gradient() function instead.

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, radial-gradient() won't work on background-color and other properties that use the <color> data type.

Composition of a radial gradient

A radial gradient is defined by a center point, an ending shape, and two or more color-stop points.

To create a smooth gradient, the radial-gradient() function draws a series of concentric shapes radiating out from the center to the ending shape (and potentially beyond). The ending shape may be either a circle or an ellipse.

Color-stop points are positioned on a virtual gradient ray that extends horizontally from the center towards the right. Percentage-based color-stop positions are relative to the intersection between the ending shape and this gradient ray, which represents 100%. Each shape is a single color determined by the color on the gradient ray it intersects.

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.<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 keywords 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

radial-gradient(
? [ [ circle || <length> ]                         [ at <position> ]? , |
?   [ ellipse || [ <length> | <percentage> ]{2} ]  [ at <position> ]? , |
    [ [ circle | ellipse ] || <extent-keyword> ]   [ at <position> ]? , |
?   at <position> ,
? ]?
  <color-stop> [ , <color-stop> ]+
)
where <extent-keyword> = closest-corner | closest-side | farthest-corner | farthest-side
  and <color-stop>     = <color> [ <percentage> | <length> ]?

Example 1

Using the following CSS we can get an ellipse background in the farthest-corner at 45px 45px, changing color from Turquoise (#00FFFF), to White, to Blue (#0000FF):

body {
  width: 100vh;
  height: 100vh;
  background-image: radial-gradient(ellipse farthest-corner at 45px 45px , #00FFFF 0%, rgba(0, 0, 255, 0) 50%, #0000FF 95%);
}

Example 2

This will produce an ellipse background in the farthest-corner at 470px 45px, changing color from Yellow (#FFFF80), to Pale Maroon, to Pale Blue (#E6E6FF):

body {
  width: 100vh;
  height: 100vh;
  background-image: radial-gradient(ellipse farthest-corner at 470px 47px , #FFFF80 20%, rgba(204, 153, 153, 0.4) 30%, #E6E6FF 60%);
}

Example 3

This will produce an ellipse background in the farthest-corner at 45px 45px, changing color from Red (#FF0000) to Blue (#0000FF):

body {
  width: 100vh;
  height: 100vh;
  background-image: radial-gradient(farthest-corner at 45px 45px , #FF0000 0%, #0000FF 100%);
}

Example 4

This will produce a fuzzy circle with a 16px radius:

body {
  width: 100vh;
  height: 100vh;
  background-image: radial-gradient(16px at 60px 50% , #000000 0%, #000000 14px, rgba(0, 0, 0, 0.3) 18px, rgba(0, 0, 0, 0) 19px); 
}

Specifications

Specification	Status	Comment
CSS Image Values and Replaced Content Module Level 3The definition of 'radial-gradients()' in that specification.	Candidate Recommendation	Initial definition.

浏览器兼容性

Feature	Firefox (Gecko)	Chrome	Internet Explorer	Opera	Safari
Basic support (on background and background-image)	3.6 (1.9.2)-moz1 16 (16)	10.0 (534.16)-webkit2	10.03	11.60-o	5.1-webkit2
On border-image	29 (29)	(Yes)	(Yes)	(Yes)	(Yes)
On any other property that accept <image>	No support	(Yes)	(Yes)	(Yes)	(Yes)
Legacy webkit syntax	No support	3-webkit2	No support	No support	4.0-webkit2
at syntax (final standard syntax)	10 (10)-moz1 16 (16)4	26	10.0	11.60-o2 2.12	No support
Interpolation hints/gradient midpoints (a percent without a color)	36 (36)	40	?	27	?

Feature	Android	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile
Basic support (on background and background-image)	(Yes)	1.0 (1.9.2)-moz1 16.0 (16)	10	(Yes)	(Yes)
On border-image	(Yes)	29.0 (29)	(Yes)	(Yes)	(Yes)
On any other property that accept <image>	No support	(Yes)	(Yes)	(Yes)	(Yes)
Legacy webkit syntax	?	No support	?	?	?
at syntax (final standard syntax)	?	10.0 (10)-moz1 16.0 (16)	10	?	?

本文档系腾讯云开发者社区成员共同维护，如有问题请联系 cloudcommunity@tencent.com

最后更新于：2017-12-18