利用JS将图标字体渲染为图片的方法详解
目录
前言
实现方式
html
css
js
效果
前言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 File/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。
htmlhtml 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" rel="external nofollow" >
<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" rel="external nofollow" >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>
css
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,提取码：1234
@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;
}
js
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();
});
效果
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。
到此这篇关于利用JS将图标字体渲染为图片的方法详解的文章就介绍到这了,更多相关JS图标字体渲染内容请搜索软件开发网以前的文章或继续浏览下面的相关文章希望大家以后多多支持软件开发网！
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