CSS3学习之radial-gradient（径向渐变）

转自：http://www.cnblogs.com/rainman/p/5133685.html

1、语法

径向渐变不同于线性渐变，线性渐变是从“一个方向”向“另一个方向”的颜色渐变，而径向渐变是从“一个点”向四周的颜色渐变。其语法如下：

background: radial-gradient(center, shape, size, start-color, ..., last-color);

center：渐变起点的位置，可以为百分比，默认是图形的正中心。
shape：渐变的形状，ellipse表示椭圆形，circle表示圆形。默认为ellipse，如果元素形状为正方形的元素，则ellipse和circle显示一样。
size：渐变的大小，即渐变到哪里停止，它有四个值。 closest-side：最近边； farthest-side：最远边； closest-corner：最近角； farthest-corner：最远角

例1：多颜色点均匀分布

div { background: radial-gradient(red, green, blue); }

以中心（50% 50%）为起点，到最远角（farthest-corner），从red到green、blue的均匀渐变，效果如下图：

完整的代码可以写成：

div { background: -webkit-radial-gradient(50% 50%, farthest-corner, red, green, blue); }

或

div { background: -webkit-radial-gradient(center, farthest-corner, red, green, blue); }

例2：多颜色节点不均匀分布

div { background: radial-gradient(red 5%, green 15%, blue 60%); }

例3：设置渐变形状

shape 参数定义了形状。它可以是值 circle 或 ellipse。其中，circle 表示圆形，ellipse 表示椭圆形。默认值是 ellipse。

div { background: radial-gradient(circle, red, yellow, green); }

div { background: radial-gradient(ellipse, red, yellow, green); }

circle：渐变为最大的圆形； ellipse：根据元素形状渐变，元素为正方形是显示效果与circle无异。

例4：不同尺寸的渐变

size指定了渐变的大小，即渐变到哪里停止，它有四个值。 closest-side：最近边； farthest-side：最远边； closest-corner：最近角； farthest-corner：最远角

div { background: radial-gradient(60% 40%, closest-side, blue, green, yellow, black); }

div { background: radial-gradient(60% 40%, farthest-side, blue, green, yellow, black); }

div { background: radial-gradient(60% 40%, closest-corner, blue, green, yellow, black); }

div { background: radial-gradient(60% 40%, farthest-corner, blue, green, yellow, black); }

效果图如下，分别用“红色”描出了不同属性指定的渐变终点：

例5：重复性渐变

repeating-radial-gradient() 函数用于重复径向渐变

div { background: repeating-radial-gradient(red, yellow 10%, green 20%); }

例6：扩展-设置方向

 div{ width: 100px; height: 100px; background: -moz-radial-gradient(bottom left, #fff 0%, #fff 60%, green 60%, green 100%);}

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随着宽、高及位置的变换可演变成：

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