1.线性渐变：linear-gradient

语法：<linear-gradient> = linear-gradient([ [ <angle> | to <side-or-corner] ,]? <color-start>[, <color-end>]+)

<side-or-corner> = [left | right] || [top | bottom]

<color-start|end> = <color>[ <length>|<percentage>]?

下述值用来表示渐变的方向，可以使用角度或者关键字来设置

  <angle>：

用角度值指定渐变的方向（或角度）。

        to left：

设置渐变为从右到左。相当于: 270deg

        to right：

设置渐变从左到右。相当于: 90deg

        to top：

设置渐变从下到上。相当于: 0deg

        to bottom：

设置渐变从上到下。相当于: 180deg。这是默认值，等同于留空不写。

 <color-start|end>用于指定渐变的起止颜色：

         <color>：指定颜色。

       <length>：

用长度值指定起止色位置。不允许负值

       <percentage>：

用百分比指定起止色位置。

示例：

div {width: 200px;height: 100px;margin: 10px 5px;border: 1px solid #ddd000;
}
#LinearStartToEnd {float:left;background: linear-gradient(#ff0000, #00ff00);
}
#LinearPercentage {float:left;background: linear-gradient(#0000ff, #ff0000 52%, #00ff00);
}
#LinearAnglePercentage {float:left;background: linear-gradient(90deg, #ff0000 20%, #00ff00 50%, #000000 80%);
}
#LinearAngle {float:left;background: linear-gradient(30deg, #ffff00 30%, #ff0000, #00ff00);
}
#LinearTopRight {float:left;background: linear-gradient(to right top, #00ff00, #ff0000 50%, #0000ff);
}

2.径向渐变：radial-gradient

     语法：

<position> = [ <length>① | <percentage>① | left | center① | right ]? [ <length>② | <percentage>② | top | center② | bottom ]?

<shape> = circle | ellipse

<size> = <extent-keyword>|[<circle-size>||<ellipse-size>]

<extent-keyword> = closest-side | closest-corner | farthest-side | farthest-corner

<circle-size> = <length>

<ellipse-size> = [ <length>| <percentage> ]{2}

<shape-size> = <length>| <percentage>

<radial-gradient> = radial-gradient([ [ <shape>|| <size> ] [ at <position> ]? , | at <position> , ]?<color-start>[[ , <color-end>]]+)

<position> 确定圆心的位置。如果提供2个参数，第一个表示横坐标，第二个表示纵坐标；如果只提供一个，第二值默认为50%，即center
         <length>①：用长度值指定径向渐变圆心的横坐标值。可以为负值。

<percentage>①：用百分比指定径向渐变圆心的横坐标值。可以为负值。

<length>②：用长度值指定径向渐变圆心的纵坐标值。可以为负值。

<percentage>②：用百分比指定径向渐变圆心的纵坐标值。可以为负值。
              center①：设置中间为径向渐变圆心的横坐标值。

center②：设置中间为径向渐变圆心的纵坐标值。

left：设置左边为径向渐变圆心的横坐标值。
              right：设置右边为径向渐变圆心的横坐标值。
              top：设置顶部为径向渐变圆心的纵坐标值。
              bottom：设置底部为径向渐变圆心的纵坐标值。
         <shape> 确定圆的类型
              circle：指定圆形的径向渐变

ellipse：指定椭圆形的径向渐变。
         <extent-keyword> circle | ellipse 都接受该值作为 size。
              closest-side：指定径向渐变的半径长度为从圆心到离圆心最近的边。
              closest-corner：指定径向渐变的半径长度为从圆心到离圆心最近的角。
              farthest-side：指定径向渐变的半径长度为从圆心到离圆心最远的边。
              farthest-corner：指定径向渐变的半径长度为从圆心到离圆心最远的角。
         <circle-size>circle 接受该值作为 size。
              <length>：用长度值指定正圆径向渐变的半径长度。不允许负值。
         <ellipse-size>ellipse 接受该值作为 size。
             <length>：用长度值指定椭圆径向渐变的横向或纵向半径长度。不允许负值。
             <percentage>：用百分比指定椭圆径向渐变的横向或纵向半径长度。不允许负值。

示例：

#RadialCenterCircle {float:left;background: radial-gradient(circle at center, #ff0000, #ffff00, #00ffff);
}
#RadialClosestSide {float:left;background: radial-gradient(circle closest-side, #ff0000, #00ff00, #ffff00);
}
#RadialFarthestSide {float:left;background: radial-gradient(farthest-side, #ff0000 20%, #ffff00 60%, #00ff00 80%);
}
#RadialRightTop {float:left;background: radial-gradient(at right top, #ff0000, #ffff00, #00ff00);
}
#RadialRadiusCenter {float:left;background: radial-gradient(farthest-side at top right, #ff0000, #ffff00, #01fefe);
}
#RadialGroup {float:left;background:radial-gradient(farthest-side at top right, #ff0000, #ffff00, #009f00, transparent),radial-gradient(60px at top left, #ff0000, #ffff00, #00ff0e);
}

       3.重复的线性渐变：repeating-linear-gradient

语法和参数类似线性渐变，这里不在赘述。详情请参考CSS手册。

示例：

#RepeatingLinearPercentage{float:left;background: repeating-linear-gradient(#ff0000, #00ff00 10%, #000000 15%);
}
#RepeatingLinearRight {float:left;background: repeating-linear-gradient(to right, #ff0000, #00ff00 10%, #000000 15%);
}
#RepeatingLinearAngle {float:left;background: repeating-linear-gradient(45deg, #ff0000, #00ff00 10%, #0000ff 15%);
}
#RepeatingLinearBottomLeft {float:left;background: repeating-linear-gradient(to bottom left, #00ffff, #ff0000 10%, #00ff00 15%);
}

3.重复的径向渐变：repeating-radial-gradient

语法和参数类似径向渐变，这里不在赘述。详情请参考CSS手册。

示例：

#RepeatingRadialCircle {float:left;background: repeating-radial-gradient(circle, #ff0000 0, #00ff00 10%, #0000ff 15%);
}
#RepeatingRadialTopLeft {float:left;background: repeating-radial-gradient(at top left, #ff0000, #00ff00 10%, #0de0f0 15%, #ffff00 20%, #000000 25%);
}
#RepeatingRadialClosestCorner {float:left;background: repeating-radial-gradient(circle closest-corner at 20px 50px, #00ff00, #ff0000 10%, #00ffff 20%, #ffff00 30%, #ff00ff 40%);
}

完整的例子：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>ImageCSS3</title>
<style>
div {width: 200px;height: 100px;margin: 10px 5px;border: 1px solid #ddd000;
}
#LinearStartToEnd {float:left;background: linear-gradient(#ff0000, #00ff00);
}
#LinearPercentage {float:left;background: linear-gradient(#0000ff, #ff0000 52%, #00ff00);
}
#LinearAnglePercentage {float:left;background: linear-gradient(90deg, #ff0000 20%, #00ff00 50%, #000000 80%);
}
#LinearAngle {float:left;background: linear-gradient(30deg, #ffff00 30%, #ff0000, #00ff00);
}
#LinearTopRight {float:left;background: linear-gradient(to right top, #00ff00, #ff0000 50%, #0000ff);
}#RadialCenterCircle {float:left;background: radial-gradient(circle at center, #ff0000, #ffff00, #00ffff);
}
#RadialClosestSide {float:left;background: radial-gradient(circle closest-side, #ff0000, #00ff00, #ffff00);
}
#RadialFarthestSide {float:left;background: radial-gradient(farthest-side, #ff0000 20%, #ffff00 60%, #00ff00 80%);
}
#RadialRightTop {float:left;background: radial-gradient(at right top, #ff0000, #ffff00, #00ff00);
}
#RadialRadiusCenter {float:left;background: radial-gradient(farthest-side at top right, #ff0000, #ffff00, #01fefe);
}
#RadialGroup {float:left;background:radial-gradient(farthest-side at top right, #ff0000, #ffff00, #009f00, transparent),radial-gradient(60px at top left, #ff0000, #ffff00, #00ff0e);
}#RepeatingLinearPercentage{float:left;background: repeating-linear-gradient(#ff0000, #00ff00 10%, #000000 15%);
}
#RepeatingLinearRight {float:left;background: repeating-linear-gradient(to right, #ff0000, #00ff00 10%, #000000 15%);
}
#RepeatingLinearAngle {float:left;background: repeating-linear-gradient(45deg, #ff0000, #00ff00 10%, #0000ff 15%);
}
#RepeatingLinearBottomLeft {float:left;background: repeating-linear-gradient(to bottom left, #00ffff, #ff0000 10%, #00ff00 15%);
}#RepeatingRadialCircle {float:left;background: repeating-radial-gradient(circle, #ff0000 0, #00ff00 10%, #0000ff 15%);
}
#RepeatingRadialTopLeft {float:left;background: repeating-radial-gradient(at top left, #ff0000, #00ff00 10%, #0de0f0 15%, #ffff00 20%, #000000 25%);
}
#RepeatingRadialClosestCorner {float:left;background: repeating-radial-gradient(circle closest-corner at 20px 50px, #00ff00, #ff0000 10%, #00ffff 20%, #ffff00 30%, #ff00ff 40%);
}</style>
</head>
<body>
<!-- 指定线性渐变起止色 -->
<div id="LinearStartToEnd"></div>
<!-- 指定线性渐变起止色位置 -->
<div id="LinearPercentage"></div>
<!-- 指定线性渐变颜色渐变方向和起止色位置 -->
<div id="LinearAnglePercentage"></div>
<!-- 指定线性渐变颜色渐变方向 -->
<div id="LinearAngle"></div>
<!-- 设置渐变从右上到左下 -->
<div id="LinearTopRight"></div><!-- 浮动Div换行，此处指定Div宽高和边界，是为了覆盖前面定义的Div统一CSS样式，可以尝试去掉指定的Div宽高和边界，看看效果 -->
<div style="width:0; height:0; border:none; clear:both"></div>
<!-- 以中心点为圆心的圆形径向渐变 -->
<div id="RadialCenterCircle"></div>
<!-- 径向渐变半径长度：圆心到离圆心最近边的长度 -->
<div id="RadialClosestSide"></div>
<!-- 径向渐变半径长度：圆心到离圆心最远边的长度 -->
<div id="RadialFarthestSide"></div>
<!-- 左边为径向渐变圆心的横坐标值,顶边为径向渐变圆心的纵坐标值 -->
<div id="RadialRightTop"></div>
<!-- 同时指定径向渐变的圆心和半径 -->
<div id="RadialRadiusCenter"></div>
<!-- 径向渐变组合 -->
<div id="RadialGroup"></div><div style="width:0; height:0; border:none; clear:both"></div>
<!-- 指定颜色起止色位置的重复线性渐变 -->
<div id="RepeatingLinearPercentage"></div>
<!-- 从左到右渐变的重复线性渐变 -->
<div id="RepeatingLinearRight"></div>
<!-- 渐变角度为45度的重复线性渐变 -->
<div id="RepeatingLinearAngle"></div>
<!-- 从左下到右上的重复线性渐变 -->
<div id="RepeatingLinearBottomLeft"></div><div style="width:0; height:0; border:none; clear:both"></div>
<!-- 圆形重复径向渐变 -->
<div id="RepeatingRadialCircle"></div>
<!-- 渐变方向为左上到右下的重复径向渐变 -->
<div id="RepeatingRadialTopLeft"></div>
<!-- 重复径向渐变：渐变半径长度为从圆心到离圆心最近的角的距离 -->
<div id="RepeatingRadialClosestCorner"></div></body>
</html>

参考：CSS参考手册：http://css.doyoe.com/