Detailed implementation example of CSS translucent border (picture)
1. Translucent border
Question:
If we want to set a red background and a black translucent border for a container, we might write like this:
border: 20px solid rgba(0,0,0,0.5); background: red;
But the effect is like this (picture 1-1.png); Why does our translucent color not implement a translucent border?
Figure 1-1.png
Solution:
We can pass background-clipAttribute To adjust the default behavior above, set its value to padding-box, and then the effect we want will appear (Figure 1-2.png);
border: 20px solid rgba(0,0,0,0.5); background: red; background-clip: padding-box;
Figure 1-2.png
2.background-clip
Since the background-clip attribute is used, let's take a look at this attribute;
background-clip:
Set the background of the element (backgroundPicture or color) extends below the border.
| Values (values) | Description |
|---|---|
| border-box | Default initial value, the background extends to the outer edge of the border (but under the border) |
| padding-box | Nothing under the border Background, that is, the background extends to the inner margin outer edge |
| content-box | The background is cropped to the outer edge of the content area (content-box) |
| text | ExperimentAPI, the background is cropped into the foreground text. |
示例
CSS content
span {
border: 10px blue;
border-style: dotted double;
margin: 1em;
padding: 2em;
background: #F8D575;
}
.border-box { background-clip: border-box; }
.padding-box { background-clip: padding-box; }
.content-box { background-clip: content-box; }
.text { background-clip: text; }
HTML content
<span class="border-box">border-box</span> <span class="padding-box">padding-box</span> <span class="content-box">content-box</span> <span class="text">text</span>
效果：（图2-1.png）
图2-1.png
3.border-style
4.border-image
初始值：
border-image-source: none
border-image-slice: 100%
border-image-width: 1
border-image-outset: 0s
border-image-repeat: stretch
4.1 border-image-source: none |
where
where
Gradient示例：
CSS content
.gradient {
border: 30px solid;
border-image-source: linear-gradient(to right, red, green, blue);
/*border-image-source: linear-gradient(90deg, red, green, blue);*/
border-image-slice: 10;
padding: 20px;
}
HTML content
<p class="gradient">The image is stretched to fill the area.</p>
效果：（图4-1.png）
图4-1.png
4.2 border-image-slice: [
这个 border-imge-slice 属性传入1~4个参数（number没有单位专指像素或百分比值）将图片分割成9个部分,1,2,3,4四个区块是不会拉伸,不会平铺，称之为盲区，5,6,7,8四个区块可以通过 border-image-repeat 来控制拉伸平铺和重复（ stretch:默认值,拉伸; repeat:平铺; round:整数次平铺; ），第9区块不显示，传入参数 fill 则显示第9区块，分割情况如下图（图4-2.png && 图2-3.png）:
图4-2.png
图4-3.png
我们通过上面这张图片（81px^81px）来看传入不同个数的参数是如何分割这张图片的；
1个参数
/* border-image-slice: slice */ border-image-slice: 27; border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png));
图4-4.png
图4-5.png(效果图)
2个参数（参考图4-3.png）
/* border-image-slice: vertical horizontal */ border-image-slice: 40 40.5; border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png));
图4-6.png
图4-7.png(效果图)
3个参数
/* border-image-slice: top horizontal bottom */ border-image-slice: 27 40 27; border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png));
图4-8.png（效果图）
4个参数(参考图4-2.png)
/* border-image-slice: top right bottom left */ border-image-slice: 27 40 27 27; border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png));
图4-9.png（效果图）
4.3 border-image-width: [
语法：
border-image-width: all /* One-value syntax */ E.g. border-image-width: 3; border-image-width: vertical horizontal /* Two-value syntax */ E.g. border-image-width: 2em 3em; border-image-width: top horizontal bottom /* Three-value syntax */ E.g. border-image-width: 5% 15% 10%; border-image-width: top right bottom left /* Four-value syntax */ E.g. border-image-width: 5% 2em 10% auto;
设置边框图片的width，如果超出了设置的border-width,会向内扩展；查看下方示例，比较（图4-10.png && 图4-11.png）；
示例：
border: 30px solid transparent;
padding: 20px;
border-image-source: url("https://mdn.mozillademos.org/files/4127/border.png");
border-image-slice: 27;
图4-10.png
border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png)); border-image-slice: 27; border-image-width: 1 2 1 1;
图4-11.png
4.4 border-image-outset: [
语法：
/* border-image-outset: sides */ border-image-outset: 30%; /* border-image-outset:vertical horizontal */ border-image-outset: 10% 30%; /* border-image-outset: top horizontal bottom */ border-image-outset: 30px 30% 45px; /* border-image-outset:top right bottom left */ border-image-outset: 7px 12px 14px 5px;
效果是将边框图片延伸到盒子外面，查看下放示例，比较（图4-12.png && 图4-13.png）；
示例:
border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png)); border-image-slice: 27; margin: 60px;
图4-12.png
border: 30px solid transparent; padding: 20px; border-image-source:url([https://mdn.mozillademos.org/files/4127/border.png](https://mdn.mozillademos.org/files/4127/border.png)); border-image-slice: 27; margin: 60px; border-image-outset: 2 1 1 1;
图4-13.png
4.4 border-image-repeat: [ stretch | repeat | round ]{1,2}
| 值（value） | 说明 |
|---|---|
| stretch | 默认初始值 ，；拉伸 |
| repeat | 平铺 |
| round | 整数次平铺 |
语法：
border-image-repeat: type /* One-value syntax */ E.g. border-image-value: stretch; border-image-repeat: horizontal vertical /* Two-value syntax */ E.g. border-image-width: round space;
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