CSS 属性：border-image
由图像组成的边框。
一个简写属性，用于组合
可能的值
背景特性子值列表。可能的子值遵循与相应先前属性可能值相同的规则。子值列表遵循特定格式
[source] [slice] / [width] / [outset] [repeat]
完整示例：url("b.png") 33% fill / 10px 20px / 0.1 space
并非所有值都是必需的——任何其他被排除的值将默认为其初始值。“/”也仅用于前置宽度和外延部分。
基本示例：url("b.png") 33% space
inherit、initial 或 unset 也可以单独使用。
示例
aside {
border: 10px solid fuchsia;
border-image: url("fluffy.png") 13 30 7 1 fill repeat;
}
/* - Establishes a 10-pixel wide border with a solid fuchsia-colored fallback.
- Sets "fluffy.png" as the border image.
- The image is sliced 13 pixels in from the top, 30 pixels in from the right, 7 pixels in from the bottom, 1 pixel in from the left and the middle portion is preserved.
- Finally, the border image sides are set to repeat. */