最近折腾了一下 useragent 插件里的设备图标，把常见设备的 PNG 基本都替换成了 SVG。最大的感受就是：在手机、Retina 屏这类高 DPI 设备上，SVG 的显示效果确实会清晰很多，边缘不会再有明显发虚的问题。

很多图标我都是直接在 iconfont上找的，毕竟现成资源比较多。不过也有不少设备品牌根本找不到合适的图标。

本着“没有就自己造”的原则，我发挥了一下主观能动性，并把这些图标的制作和优化分成了两个方向。

纯色 SVG 图标

像荣耀（HONOR）、OPPO、vivo、三星（SAMSUNG）这类品牌，如果直接使用完整的字母 Logo，在 useragent 这种小尺寸场景下实际显示会特别小，可读性并不好。后来我换了个思路：直接参考它们官网favicon来重绘图标。这样既能保留品牌辨识度，小尺寸下看起来也更加清晰。

当然，自己做 SVG 也不一定非得从零开始。一个比较偷懒但实用的方法是：

• 先把图标保存为透明 PNG（最好是纯色的不要有渐变，渐变可以用下文的代码实现）
• 再通过 PNG 转 SVG 工具进行矢量化，比如 PNG to SVG 、 PNG转SVG

虽然这种方式生成的 SVG 精度会比手工绘制稍差一点，但用在 useragent 这种尺寸很小的设备信息展示里，其实已经完全够用了。

渐变 SVG 图标

真正比较麻烦的，其实是带渐变色的图标。iconfont 也不支持上传有渐变代码的SVG图标。

很多在 iconfont 上看起来像“渐变”的图标，本质上其实是多个纯色色块拼接出来的。尺寸小的时候还好，但放大之后会发现过渡并不自然，有些甚至会出现明显的断层感。

后来想着，既然 SVG 本身支持渐变，那不如直接用代码实现。

AI 很快给了答案：使用 <defs> 配合 <linearGradient> 定义渐变。

例如：

<defs>
<linearGradient id="gradient" x1="0%" y1="100%" x2="100%" y2="0%">
	<stop offset="0%" style="stop-color:#F8672C;stop-opacity:1" />
	<stop offset="50%" style="stop-color:#90C300;stop-opacity:1" />
	<stop offset="100%" style="stop-color:#0881d8;stop-opacity:1" />
</linearGradient>
</defs>

这里的 <defs> 用来存储可复用的图形元素、样式、滤镜、渐变等内容，而 <linearGradient> 则定义线性渐变。

其中：x1 y1 ：渐变起点；x2 y2 ：渐变终点

本质上，它们定义的是“渐变线”的方向。

常见方向大概如下：

然后通过 fill="url(#gradient)" 来引用对应的渐变。

其中 gradient 就是前面定义的 id，当然也可以定义多套渐变，分别用于不同路径。

Windows 11的图标

我会让左上角颜色稍微淡一点，这样会更接近官方图标的视觉效果。

<svg class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" width="128" height="128" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<linearGradient id="gradient_win8" x1="0%" y1="0%" x2="100%" y2="100%">
<stop offset="0%" style="stop-color:#4dd0fd;stop-opacity:1" />
<stop offset="50%" style="stop-color:#1e9ae4;stop-opacity:1" />
<stop offset="100%" style="stop-color:#0179d3;stop-opacity:1" />
</linearGradient>
</defs>
<path d="M538.624 538.648h485.352V1024H538.624z m-538.6 0h485.352V1024H0.024zM538.624 0h485.352v485.352H538.624zM0.024 0h485.352v485.352H0.024z" fill="url(#gradient_win8)"></path></svg>

QQ邮箱的图标

它的图标则更有意思，渐变层次很明显，而且由 3 段路径组成，中间两块区域相对更小。所以我最后定义了两套渐变色：

• 外层使用跨度较大的渐变
• 中间区域使用颜色跨度更短的渐变

这样缩小之后，整体的颜色过渡会自然很多，不会出现“中间突然变色”的情况。

<svg class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" width="128" height="128" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<linearGradient id="gradient_qqmail1" x1="100%" y1="0%" x2="0%" y2="100%">
<stop offset="0%" style="stop-color:#cff016;stop-opacity:1" />
<stop offset="50%" style="stop-color:#f8c30b;stop-opacity:1" />
<stop offset="100%" style="stop-color:#ff6a00;stop-opacity:1" />
</linearGradient>
<linearGradient id="gradient_qqmail2" x1="100%" y1="0%" x2="0%" y2="100%">
<stop offset="0%" style="stop-color:#e5e412;stop-opacity:1" />
<stop offset="50%" style="stop-color:#f8c30b;stop-opacity:1" />
<stop offset="100%" style="stop-color:#ff9002;stop-opacity:1" />
</linearGradient>
</defs>
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IE的图标

IE11的图标可以理解为径向渐变，中心亮→边缘暗。

<svg class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" width="128" height="128" 
xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<radialGradient id="gradient_ie11" cx="50%" cy="50%" r="50%">
<stop offset="0%" style="stop-color:#9bf6fc;stop-opacity:1" />
<stop offset="30%" style="stop-color:#8df1fc;stop-opacity:1" />
<stop offset="100%" style="stop-color:#40bbea;stop-opacity:1" />
</radialGradient>
</defs>
<path d="M970.43 687.21c-64.64 0-129.29 0.61-193.91-0.39-18.57-0.29-29.87 4.93-41.8 20.42-53.34 69.22-124.92 96.66-209.99 76.83-82.91-19.32-134.04-73.96-153.67-157.12-2.28-9.66-2.37-19.83-3.7-31.71h32.02c198.77 0 397.53-0.27 596.29 0.43 16 0.06 23.2-3.52 26-15.55 1.51-15 2.29-30.21 2.32-45.6-0.25-44.76-6.38-88.34-18.63-130.9-14.25-48.42-36.25-93.52-64.57-133.87C890 199.46 828.04 148.4 752.31 113.79 694.54 87.77 630.45 73.3 562.96 73.3h-0.15c-0.62 0.04-1.25 0.08-1.87 0.1-195.9 9.16-336.19 101.82-419.18 279.5-12.75 27.3-19.74 57.29-29.4 86.04l5.92 3.32c57.1-75.43 125.98-137.45 205.86-186.96 1.59 1.4 3.18 2.81 4.78 4.21-5.8 6.33-11.57 12.69-17.39 19-75.79 82.08-146.93 167.75-203.84 264.37a858.76 858.76 0 0 0-5.39 9.27c2.13 53.76 13.51 105.15 32.57 152.63 0.34-0.52 0.66-1.05 1-1.57 40.01 94.38 101.75 168.59 193.2 226.2-0.32 0.13-0.63 0.25-0.95 0.38a457.524 457.524 0 0 0 44.73 23.27c4.18 0.85 8.51 2.24 13.14 4.2 129.77 54.87 270.74 45.42 387.34-13.98C869.74 893.83 946.42 811.44 988.48 711c2.78-7.03 5.52-14.62 9.08-23.8h-27.13zM556.99 280.64c108.64-6.04 202.01 69 215.87 176.43h-401.7c2.04-87.93 90.44-171.12 185.83-176.43z" fill="url(#gradient_ie11)"></path><path d="M1009.88 195.95c16.88-84.44-19.14-154.26-94.05-175.8-33.95-9.76-71.89-11.41-107.41-8.71-68.58 5.19-134.19 25.08-198.08 50.63-0.01 0-0.01 0-0.02 0.01-3.35 1.16-6.85 2.52-10.5 4.07-11.79 4.09-24.58 6.43-37 7.16h0.15c6.91 0 13.77 0.16 20.61 0.46-94.52 48.03-254.64 185.76-254.64 185.76s-146.53 144.1-226.63 292.62C49.2 644.49 11.87 742.49 1.22 849.42c-10.3 103.32 45.3 163.21 148.64 164.29 68.09 0.72 127.25-27.19 186.47-54.88 13.05-6.1 24.08-8.31 36.54-5.76a461.938 461.938 0 0 1-44.73-23.27c-40.91 16.25-74.79 33.17-110.61 43.03-65.86 18.12-123.59-23.71-131.91-91.75-6.24-51 12.3-119.14 49.26-176.3 0.33-0.52 0.67-1.03 1-1.56 235.04-422.5 584.91-572.24 606.72-593.66 3.25 1.37 6.49 2.78 9.7 4.23a492.96 492.96 0 0 0-9.63-4.29c40.12-35.95 142.38-49.37 188.24-25.34 40.36 21.14 60.42 68.13 49.68 121.07-5.6 27.59-14.28 54.57-23.37 88.58a579.372 579.372 0 0 0-16.45-24.04c28.32 40.36 50.32 85.46 64.57 133.87-6.28-21.8-14.15-43.33-23.67-64.62-4.62-10.32-4.71-24.68-1.91-35.93 8.96-36 22.87-70.88 30.12-107.14z" fill="#ffc124"></path></svg>

IE8的图标，他的扩展不是从中心发散的，有一些偏下，类似椭圆。椭圆渐变在 SVG 中没有直接的 <ellipseGradient> 标签，需要用 radialGradient + gradientUnits="objectBoundingBox" 配合不同的 rx/ry 来实现，或者通过 gradientTransform 拉伸。

<svg class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" width="128" height="128" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<radialGradient id="gradient_ie8" cx="50%" cy="50%" r="70%" gradientUnits="objectBoundingBox" gradientTransform="scale(1, 1.5)">
<stop offset="0%" style="stop-color:#82e5fa;stop-opacity:1" />
<stop offset="20%" style="stop-color:#39bbf5;stop-opacity:1" />
<stop offset="70%" style="stop-color:#005cb0;stop-opacity:1" />
<stop offset="100%" style="stop-color:#003269;stop-opacity:1" />
</radialGradient>
</defs>
<path d="M970.43 687.21c-64.64 0-129.29 0.61-193.91-0.39-18.57-0.29-29.87 4.93-41.8 20.42-53.34 69.22-124.92 96.66-209.99 76.83-82.91-19.32-134.04-73.96-153.67-157.12-2.28-9.66-2.37-19.83-3.7-31.71h32.02c198.77 0 397.53-0.27 596.29 0.43 16 0.06 23.2-3.52 26-15.55 1.51-15 2.29-30.21 2.32-45.6-0.25-44.76-6.38-88.34-18.63-130.9-14.25-48.42-36.25-93.52-64.57-133.87C890 199.46 828.04 148.4 752.31 113.79 694.54 87.77 630.45 73.3 562.96 73.3h-0.15c-0.62 0.04-1.25 0.08-1.87 0.1-195.9 9.16-336.19 101.82-419.18 279.5-12.75 27.3-19.74 57.29-29.4 86.04l5.92 3.32c57.1-75.43 125.98-137.45 205.86-186.96 1.59 1.4 3.18 2.81 4.78 4.21-5.8 6.33-11.57 12.69-17.39 19-75.79 82.08-146.93 167.75-203.84 264.37a858.76 858.76 0 0 0-5.39 9.27c2.13 53.76 13.51 105.15 32.57 152.63 0.34-0.52 0.66-1.05 1-1.57 40.01 94.38 101.75 168.59 193.2 226.2-0.32 0.13-0.63 0.25-0.95 0.38a457.524 457.524 0 0 0 44.73 23.27c4.18 0.85 8.51 2.24 13.14 4.2 129.77 54.87 270.74 45.42 387.34-13.98C869.74 893.83 946.42 811.44 988.48 711c2.78-7.03 5.52-14.62 9.08-23.8h-27.13zM556.99 280.64c108.64-6.04 202.01 69 215.87 176.43h-401.7c2.04-87.93 90.44-171.12 185.83-176.43z" fill="url(#gradient_ie8)"></path><path d="M1009.88 195.95c16.88-84.44-19.14-154.26-94.05-175.8-33.95-9.76-71.89-11.41-107.41-8.71-68.58 5.19-134.19 25.08-198.08 50.63-0.01 0-0.01 0-0.02 0.01-3.35 1.16-6.85 2.52-10.5 4.07-11.79 4.09-24.58 6.43-37 7.16h0.15c6.91 0 13.77 0.16 20.61 0.46-94.52 48.03-254.64 185.76-254.64 185.76s-146.53 144.1-226.63 292.62C49.2 644.49 11.87 742.49 1.22 849.42c-10.3 103.32 45.3 163.21 148.64 164.29 68.09 0.72 127.25-27.19 186.47-54.88 13.05-6.1 24.08-8.31 36.54-5.76a461.938 461.938 0 0 1-44.73-23.27c-40.91 16.25-74.79 33.17-110.61 43.03-65.86 18.12-123.59-23.71-131.91-91.75-6.24-51 12.3-119.14 49.26-176.3 0.33-0.52 0.67-1.03 1-1.56 235.04-422.5 584.91-572.24 606.72-593.66 3.25 1.37 6.49 2.78 9.7 4.23a492.96 492.96 0 0 0-9.63-4.29c40.12-35.95 142.38-49.37 188.24-25.34 40.36 21.14 60.42 68.13 49.68 121.07-5.6 27.59-14.28 54.57-23.37 88.58a579.372 579.372 0 0 0-16.45-24.04c28.32 40.36 50.32 85.46 64.57 133.87-6.28-21.8-14.15-43.33-23.67-64.62-4.62-10.32-4.71-24.68-1.91-35.93 8.96-36 22.87-70.88 30.12-107.14z" fill="#f5bc22"></path></svg>

联想的图标

它是一个比较典型的案例，favicon 本身带有高光效果，而这个高光并不是简单的“左上到右下”线性渐变。

一开始我直接用：x1="0%" y1="0%" x2="100%" y2="100%"

虽然方向对了，但高光位置始终不自然。后来才发现，需要配合 gradientUnits="userSpaceOnUse" 来使用真实坐标系控制渐变位置。

当时我的 SVG 视窗定义是 viewBox="0 0 1024 1024"。在实际调试中，我靠着感觉硬调出了一组参数：x1="0%" y1="0%" x2="500" y2="1250"。视觉效果虽然完美对齐了，但具体怎么计算出来的，当时我脑子里也没什么头绪。

<svg class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" width="128" height="128" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<linearGradient id="gradient_lenovo" gradientUnits="userSpaceOnUse" x1="0%" y1="0%" x2="500" y2="1250">
<stop offset="0%" style="stop-color:#ec9796;stop-opacity:1" />
<stop offset="50%" style="stop-color:#e65752;stop-opacity:1" />
<stop offset="51%" style="stop-color:#e2231b;stop-opacity:1" />
<stop offset="100%" style="stop-color:#e2231b;stop-opacity:1" />
</linearGradient>
</defs>
<path d="M0 0h1024v1024H0V0z m312 208v576h400v-108h-280V208H312z" fill="url(#gradient_lenovo)"></path></svg>

理论上来说，x2 和 y2 似乎应该和 viewBox 有一定关系，但实际调的时候我发现并没有一个特别固定的公式。

尤其是一些带高光、拟物感或者品牌特殊视觉风格的 Logo，很难单纯通过数学计算直接得出“正确答案”，最后往往还是需要靠肉眼慢慢调整。

不过也正因为这样，SVG 渐变其实比想象中灵活很多。

以前总觉得 SVG 只是“矢量图”，真正折腾之后才发现，它更像是一套完整的绘图语言。很多过去只能在 PS 里做的效果，现在直接写代码也能实现，而且还能无限缩放、不失真。

对于 useragent 这种本身图标尺寸很小、但显示场景又特别多的插件来说，SVG 确实是个很合适的方案。