在软件开发中肯定要用到图标，比如下图的 Groove 音乐中就用到了许多图标。一种获取这些图标的方法是把 Groove 音乐截个图，然后熟练地开启 Photoshop，开始抠图。这种方式很逊，效率也很低（虽然我刚开始就是这么干的）。
如果打开 C:/Program Files/WindowsApps（需要修改权限才能进入），可以发现几个名字里带 ZuneMusic 的文件夹，其中的某一个文件夹中会有字体文件 SegMVR2.ttf。这是一个图标字体文件，双击安装之后，打开 Windows 自带的字符映射表应用，将字体换为 Segoe MVR MDL2 Assets，可以看到里面的字符其实就是图标。其实可以用 Metro Studio 将这些字体导出为 png、svg 等格式的图片，但是 Metro Studio 导出的字符看起来很细，也无法分别控制上下和左右的内边距，所以这里改用 Javascript 操作 canvas 绘制图标，然后导出为 png。
在 CodePen 上已经有人给出了将 Microsoft 开源的 Fabric UI Icon 渲染为 png 图片的 demo，效果很不错。阅读源代码之后可以发现，他在 getFontIconCharacter() 先创建了一个临时的元素，根据想要的图标的名字设置元素的 className，获取::before 伪元素的 content 中字符的 Unicode，接着在 drawIcon() 中使用 context.fillText() 方法绘制字符，最后 canvas.toDataURL() 就能将 canvas 的内容转换为 base64 格式的图片。
可以看到，对于自定义的的字体，我们只需知道字符的 Unicode，就能实现导出功能。
html 和 coepen 中的几乎完全一样，唯一不同的地方就是将 font-class 换成了 font-unicode，因为我们只有字符的 unicode。
<html> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" type="text/css" href="index.css"> <title>iconfont to png</title> </head> <body> <div class="ms-Grid" dir="ltr"> <h1 class="ms-font-su">Render Office Fabric UI Icons into Canvas</h1> <p>This is a simple tool to render an icon from the <a class="ms-fontColor-blueLight" href="https://developer.microsoft.com/en-us/fabric#/styles/icons">Office Fabric UI icon font</a> into an HTML <code><canvas></code> with a background color. Right-click and save the image to use it.</p> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-sm12 ms-lg6"> <h2 class="ms-font-xxl">Icon/Canvas Specifications</h2> <form id="form"> <div class="ms-Grid"> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-md6"> <label for="font-unicode">Icon unicode</label> <input type="text" name="fontClass" id="font-unicode" placeholder="e.g. ms-Icon ms-Icon-Warning" value="E768"> </div> <div class="ms-Grid-col ms-md6"> <label for="font-size">Font size (px)</label> <input type="number" step="1" min="1" name="fontSize" id="font-size" placeholder="e.g. 60" value="56"> </div> </div> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-md6"> <label for="image-width">Image width (px)</label> <input type="number" step="1" min="0" name="imageWidth" id="image-width" placeholder="e.g. 80" value="92"> </div> <div class="ms-Grid-col ms-md6"> <label for="image-height">Image height (px)</label> <input type="number" step="1" min="0" name="imageHeight" id="image-height" placeholder="e.g. 80" value="92"> </div> </div> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-md6"> <label for="left-offset">Left offset</label> <input type="number" step="1" name="leftOffset" id="left-offset" placeholder="e.g. 40" value="46"> </div> <div class="ms-Grid-col ms-md6"> <label for="top-offset">Top offset</label> <input type="number" step="1" name="topOffset" id="top-offset" placeholder="e.g. 40" value="46"> </div> </div> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-md6"> <label for="bg-color">Background color</label> <input type="text" name="bgColor" id="bg-color" placeholder="e.g. #777777" value=#777777> </div> <div class="ms-Grid-col ms-md6"> <label for="icon-color">Icon color</label> <input type="text" name="iconColor" id="icon-color" placeholder="e.g. #FFFFFF" value=#FFFFFF> </div> </div> <div class="ms-Grid-row"> <div class="ms-Grid-col ms-sm12"> <label><input type="checkbox" checked name="shape" id="shape"> Use a circle as the background fill</label> </div> </div> </div> <input type="submit" class="ms-button ms-bgColor-themeDark ms-bgColor-themeDarker--hover ms-fontColor-white" value="Render Font Icon"> <p>If the icon does not render immediately, wait a few seconds and press the <b>Render</b> button again; the webfont may still be loading.</p> </form> </div> <div class="ms-Grid-col ms-sm12 ms-lg6"> <h2 class="ms-font-xxl">Result</h2> <div class="canvas-container"> <canvas id="canvas" width="92" height="92"></canvas> </div> <p><a id="download-link" class="ms-button ms-bgColor-themeDark ms-bgColor-themeDarker--hover ms-fontColor-white" target="_blank"><i class="ms-Icon ms-Icon--Download"></i> Download the image</a></p> <label for="dataURL">Data URL</label> <input id="dataURL" type="text"> </div> </div> </div> </body> <script src="index.js"></script> </html> 与 codepen 中的代码相比，这里只是多了一个 @font-face 声明要使用的字体。图标的下载地址在 蓝奏云，密码为 abcr。
@import url(https://static2.sharepointonline.com/files/fabric/office-ui-fabric-core/11.0.0/css/fabric.min.css); @font-face { font-family: 'Segoe MVR MDL2 Assets'; src: url('SegoeMVRMDL2Assets.ttf') format('truetype'); font-weight: normal; font-style: normal; } html { box-sizing: border-box; } *, *:before, *:after { box-sizing: inherit; } body { font-family: "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; background-color: #0078d4; color: white; } .ms-Grid { margin: 0 auto; padding: 0 16px; max-width: 1280px; } .ms-Grid-row { margin-left: -16px; margin-right: -16px; } .ms-Grid-col { padding: 0 16px; } label { display: block; margin-bottom: 0.5em; } input { border: none; display: block; margin-bottom: 2em; padding: 5px; width: 100%; font-size: 16px; } input[type="checkbox"] { display: inline-block; padding: 0; width: auto; } input[type="button"], input[type="submit"], .ms-button { cursor: pointer; display: inline-block; padding: 0.75em 2em; text-decoration: none; width: auto; } .ms-button .ms-Icon { transform: translateY(2px); } .canvas-container { background-color: white; display: inline-block; margin-bottom: 1em; padding: 10px; width: auto; } #canvas { color: black; font-family: FabricMDL2Icons; } 这里我们主要修改了 getFontIconCharacter() 函数，直接根据输入框的内容返回字符的 Unicode。
const form = document.getElementById("form"); const canvas = document.getElementById("canvas"); const context = canvas.getContext("2d"); const download = document.getElementById("download-link"); const dataURL = document.getElementById("dataURL"); const fontFamily = "Segoe MVR MDL2 Assets"; function getFontIconCharacter(unicode) { return String.fromCharCode(parseInt(unicode, 16)); } function drawCircle() { var centerX = canvas.width / 2; var centerY = canvas.height / 2; var radius = canvas.width / 2; context.beginPath(); context.arc(centerX, centerY, radius, 0, 2 * Math.PI, false); context.fillStyle = document.getElementById("bg-color").value || "#777777"; context.fill(); } function drawRect() { context.fillStyle = document.getElementById("bg-color").value || "#777777"; context.fillRect(0, 0, canvas.width, canvas.height); } function drawIcon() { canvas.width = parseInt(document.getElementById("image-width").value, 10) || 92; canvas.height = parseInt(document.getElementById("image-height").value, 10) || 92; context.clearRect(0, 0, canvas.width, canvas.height); if (document.getElementById("shape").checked) { drawCircle(); } else { drawRect(); } context.fillStyle = document.getElementById("icon-color").value || "#FFFFFF"; let fontUnicode = document.getElementById("font-unicode").value, fontSize = document.getElementById("font-size").value || 280, topOffset = document.getElementById("top-offset").value || 210, leftOffset = document.getElementById("left-offset").value || 210; context.font = `${fontSize}px ${fontFamily}`; context.textAlign = "center"; context.textBaseline = "middle"; context.fillText(getFontIconCharacter(fontUnicode), parseInt(leftOffset, 10), parseInt(topOffset, 10)); dataURL.value = canvas.toDataURL(); } window.addEventListener('load', function () { drawIcon(); }); document.addEventListener('DOMContentLoaded', function () { context.font = "10px " + fontFamily; context.fillText("...", 0, 0); }); form.addEventListener("submit", function (event) { event.preventDefault(); drawIcon(); }); download.addEventListener("click", function (event) { if (typeof this.download !== "undefined") { this.href = canvas.toDataURL(); this.download = `${document.getElementById("font-unicode").value}.png`; } else { event.preventDefault(); alert("Your browser does not support downloading a canvas image. Please right-click on the image to save it."); } }); dataURL.addEventListener("focus", function (event) { dataURL.select(); }); 打开 html 之后如下图所示，只需修改 Icon unicode，再点击 Render Font Icon 按钮，就能在右侧的画布中看到图标，点击 Download the image 按钮就能下载图标了。
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