利用JS將圖標字體渲染為圖片的方法詳解

前言

在軟件開發中肯定要用到圖標,比如下圖的 Groove 音樂中就用到瞭許多圖標。一種獲取這些圖標的方法是把 Groove 音樂截個圖,然後熟練地開啟 Photoshop,開始摳圖。這種方式很遜,效率也很低(雖然我剛開始就是這麼幹的)。

如果打開 C:/Program File/WindowsApps(需要修改權限才能進入),可以發現幾個名字裡帶 ZuneMusic 的文件夾,其中的某一個文件夾中會有字體文件 SegMVR2.ttf。這是一個圖標字體文件,雙擊安裝之後,打開 Windows 自帶的字符映射表應用,將字體換為 Segoe MVR MDL2 Assets,可以看到裡面的字符其實就是圖標。其實可以用 Metro Studio 將這些字體導出為 png、svg 等格式的圖片,但是 Metro Studio 導出的字符看起來很細,也無法分別控制上下和左右的內邊距,所以這裡改用 Javascript 操作 canvas 繪制圖標,然後導出為 png。

實現方式

在 CodePen 上已經有人給出瞭將 Microsoft 開源的 Fabric UI Icon 渲染為 png 圖片的 demo,效果很不錯。閱讀源代碼之後可以發現,他在 getFontIconCharacter() 先創建瞭一個臨時的元素,根據想要的圖標的名字設置元素的 className,獲取::before偽元素的 content 中字符的 Unicode,接著在 drawIcon() 中使用 context.fillText() 方法繪制字符,最後 canvas.toDataURL() 就能將 canvas 的內容轉換為 base64 格式的圖片。

可以看到,對於自定義的的字體,我們隻需知道字符的 Unicode,就能實現導出功能。

html

html 和 coepen 中的幾乎完全一樣,唯一不同的地方就是將 font-class 換成瞭 font-unicode,因為我們隻有字符的 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>&lt;canvas&gt;</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

與 codepen 中的代碼相比,這裡隻是多瞭一個 @font-face 聲明要使用的字體。圖標的下載地址在 藍奏雲,密碼為 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;
}

js

這裡我們主要修改瞭 getFontIconCharacter() 函數,直接根據輸入框的內容返回字符的 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

打開 html 之後如下圖所示,隻需修改 Icon unicode,再點擊 Render Font Icon 按鈕,就能在右側的畫佈中看到圖標,點擊 Download the image 按鈕就能下載圖標瞭。

到此這篇關於利用JS將圖標字體渲染為圖片的方法詳解的文章就介紹到這瞭,更多相關JS圖標字體渲染內容請搜索LevelAH以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持LevelAH!

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