text-shadow

概述

text-shadow 为文字添加阴影。可以为文字与  text-decorations  添加多个阴影，阴影值之间用逗号隔开。

每个阴影指定相对文字的偏移量，可选的颜色及模糊半径。

多个阴影从前往后叠加，第一个阴影在最前面。

该属性也可以应用到伪元素::first-line与::first-letter上。

语法

/* offset-x | offset-y | blur-radius | color */
text-shadow: 1px 1px 2px black;
/* color | offset-x | offset-y | blur-radius */
text-shadow: #CCC 1px 0 10px;
/* offset-x | offset-y | color */
text-shadow: 5px 5px #558ABB;
/* color | offset-x | offset-y */
text-shadow: white 2px 5px;
/* offset-x | offset-y
/* Use defaults for color and blur-radius */
text-shadow: 5px 10px;
text-shadow: inherit;

取值

<color>

可选。可以在偏移量之前或之后指定。如果没有指定颜色，则使用UA（用户代理）自行选择的颜色。

Note: 如果想确保跨浏览器的一致性，请明确地指定一种颜色

<offset-x> <offset-y>

必选。这些长度值指定阴影相对文字的偏移量。<offset-x> 指定水平偏移量，若是负值则阴影位于文字左边。 <offset-y> 指定垂直偏移量，若是负值则阴影位于文字上面。如果两者均为0，则阴影位于文字正后方（如果设置了<blur-radius> 则会产生模糊效果)。
可用单位请查看 <length>。

<blur-radius>

可选。这是 <length> 值。如果没有指定，则默认为0。值越大，模糊半径越大，阴影也就越大越淡（wider and lighter）。

形式化语法

none | <shadow-t>#
where 
<shadow-t> = [ <length>{2,3} && <color>? ]
where 
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
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>? ] )
<named-color> = transparent | aliceblue | antiquewhite | aqua | aquamarine | azure | beige | bisque | black | blanchedalmond | blue | blueviolet | brown | burlywood | cadetblue | chartreuse | chocolate | coral | cornflowerblue | cornsilk | crimson | cyan | darkblue | darkcyan | darkgoldenrod | darkgray | darkgreen | darkgrey | darkkhaki | darkmagenta | darkolivegreen | darkorange | darkorchid | darkred | darksalmon | darkseagreen | darkslateblue | darkslategray | darkslategrey | darkturquoise | darkviolet | deeppink | deepskyblue | dimgray | dimgrey | dodgerblue | firebrick | floralwhite | forestgreen | fuchsia | gainsboro | ghostwhite | gold | goldenrod | gray | green | greenyellow | grey | honeydew | hotpink | indianred | indigo | ivory | khaki | lavender | lavenderblush | lawngreen | lemonchiffon | lightblue | lightcoral | lightcyan | lightgoldenrodyellow | lightgray | lightgreen | lightgrey | lightpink | lightsalmon | lightseagreen | lightskyblue | lightslategray | lightslategrey | lightsteelblue | lightyellow | lime | limegreen | linen | magenta | maroon | mediumaquamarine | mediumblue | mediumorchid | mediumpurple | mediumseagreen | mediumslateblue | mediumspringgreen | mediumturquoise | mediumvioletred | midnightblue | mintcream | mistyrose | moccasin | navajowhite | navy | oldlace | olive | olivedrab | orange | orangered | orchid | palegoldenrod | palegreen | paleturquoise | palevioletred | papayawhip | peachpuff | peru | pink | plum | powderblue | purple | rebeccapurple | red | rosybrown | royalblue | saddlebrown | salmon | sandybrown | seagreen | seashell | sienna | silver | skyblue | slateblue | slategray | slategrey | snow | springgreen | steelblue | tan | teal | thistle | tomato | turquoise | violet | wheat | white | whitesmoke | yellow | yellowgreen
<deprecated-system-color> = ActiveBorder | ActiveCaption | AppWorkspace | Background | ButtonFace | ButtonHighlight | ButtonShadow | ButtonText | CaptionText | GrayText | Highlight | HighlightText | InactiveBorder | InactiveCaption | InactiveCaptionText | InfoBackground | InfoText | Menu | MenuText | Scrollbar | ThreeDDarkShadow | ThreeDFace | ThreeDHighlight | ThreeDLightShadow | ThreeDShadow | Window | WindowFrame | WindowText
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>

例子

.red-text-shadow {
   text-shadow: red 0 -2px;
}

<p class="red-text-shadow">
   Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo
   inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.
</p>

.white-with-blue-shadow {
   text-shadow: 1px 1px 2px black, 0 0 1em blue, 0 0 0.2em blue;
   color: white;
   font: 1.5em Georgia, "Bitstream Charter", "URW Bookman L", "Century Schoolbook L", serif;
}

<p class="white-with-blue-shadow">
   Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore
   veritatis et quasi architecto beatae vitae dicta sunt explicabo.
</p>

.gold-on-gold {
   text-shadow: rgba(0,0,0,0.1) -1px 0, rgba(0,0,0,0.1) 0 -1px,
   rgba(255,255,255,0.1) 1px 0, rgba(255,255,255,0.1) 0 1px,
   rgba(0,0,0,0.1) -1px -1px, rgba(255,255,255,0.1) 1px 1px;
   color: gold;
   background: gold;
}

<p class="gold-on-gold">
   Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore
   veritatis et quasi architecto beatae vitae dicta sunt explicabo.
</p>

规范

The CSS property text-shadow was improperly defined in CSS2and dropped in CSS2 (Level 1). The CSS Text Module Level 3 spec improved and precised the syntax. Later it was moved to new working draft CSS Text Decoration Module Level 3.

浏览器兼容性

• Gecko (Firefox) theoretically supports infinite text-shadows (don't try it).
  Gecko 2 and later cap the blur radius at 300 for performance reasons.
  If the <color> value is unspecified, then Gecko uses the value of the element's color property.
• Opera supports a maximum of 6-9 text-shadows for performance reasons. The blur radius is limited to 100px.
  Opera 9.5-10.1 adheres to the old, reverse painting order (CSS2, the first specified shadow is on the bottom).
• Internet Explorer 5.5 supports Microsoft's Shadow andDropShadow Filter.
• Safari: Any shadows that do not explicitly specify a color are transparent.
  Safari 1.1-3.2 only supports one text-shadow (displays the first shadow of a comma-separated list and ignores the rest).
  Safari 4.0 (WebKit 528) and later support multiple text-shadows.
• Konqueror supports text-shadow starting with version 3.4.

参见

• box-shadow