WordPress script to replace images with letters: LetterAvatar

下面由WordPress技巧栏目给大家介绍关于用字母替代图片脚本：LetterAvatar，希望对需要的朋友有所帮助！

基于canvas，通过toDataURL动态生成base64图片。目前我主题的Gravatar头像，就是利用这个LetterAvatar脚本实现未设置Gravatar头像则读取ALT标签，自动生成首字图片替代默认的头像图片。

之前已有WP爱好者制作了一款：mk-letter-avatar 字母头像插件，试了一下很好用，不过打开浏览器开者工具发现产生大量404错误，看了一下源代码，该插件是通过无头像返回404错误，触发onerror事件用自动生成的字母图片替换src图片地址，判断方式不是很合理，如果不是因为个缺点我都想直接拿来用了，如果作者再优化一下，绝对是款优秀实用的插件。

我的实现原理和插件不同，配合头像本地缓存功能，判断无头像后，直接为无头像的图片添加特定的class类，然后通过LetterAvatar脚本替换图片。

需要注意的是上面提到的插件，Gravatar头像图片必须有alt标签属性，否则不会生成正常的图片，可惜大部分主题默认Gravatar头像alt标签属性是空的.....

如果想自动为Gravatar头像添加alt标签属性，可以将下面的代码添加到当前主题函数模板functions.php中：

之后，自动将评论者昵称做为alt属性。

本文只是自己做个记录，并不是教大家怎么弄这个头像，如果认为这字母头像还不错，请直接使用上面介绍的插件。

另附LetterAvatar脚本演示代码：

<script> /* * LetterAvatar * * Artur Heinze * Create Letter avatar based on Initials * based on https://gist.github.com/leecrossley/6027780 */ (function(w, d){ function LetterAvatar (name, size, color) { name = name || &#39;&#39;; size = size || 60; var colours = [ "#1abc9c", "#2ecc71", "#3498db", "#9b59b6", "#34495e", "#16a085", "#27ae60", "#2980b9", "#8e44ad", "#2c3e50", "#f1c40f", "#e67e22", "#e74c3c", "#ecf0f1", "#95a5a6", "#f39c12", "#d35400", "#c0392b", "#bdc3c7", "#7f8c8d" ], nameSplit = String(name).split(&#39; &#39;), initials, charIndex, colourIndex, canvas, context, dataURI; if (nameSplit.length == 1) { initials = nameSplit[0] ? nameSplit[0].charAt(0):&#39;?&#39;; } else { initials = nameSplit[0].charAt(0) + nameSplit[1].charAt(0); } if (w.devicePixelRatio) { size = (size * w.devicePixelRatio); } charIndex = (initials == &#39;?&#39; ? 72 : initials.charCodeAt(0)) - 64; colourIndex = charIndex % 20; canvas = d.createElement(&#39;canvas&#39;); canvas.width = size; canvas.height = size; context = canvas.getContext("2d"); context.fillStyle = color ? color : colours[colourIndex - 1]; context.fillRect (0, 0, canvas.width, canvas.height); context.font = Math.round(canvas.width/2)+"px Arial"; context.textAlign = "center"; context.fillStyle = "#FFF"; context.fillText(initials, size / 2, size / 1.5); dataURI = canvas.toDataURL(); canvas = null; return dataURI; } LetterAvatar.transform = function() { Array.prototype.forEach.call(d.querySelectorAll(&#39;img[alt]&#39;), function(img, name, color) { name = img.getAttribute(&#39;alt&#39;); color = img.getAttribute(&#39;color&#39;); img.src = LetterAvatar(name, img.getAttribute(&#39;width&#39;), color); img.removeAttribute(&#39;avatar&#39;); img.setAttribute(&#39;alt&#39;, name); }); }; // AMD support if (typeof define === &#39;function&#39; && define.amd) { define(function () { return LetterAvatar; }); // CommonJS and Node.js module support. } else if (typeof exports !== &#39;undefined&#39;) { // Support Node.js specific `module.exports` (which can be a function) if (typeof module != &#39;undefined&#39; && module.exports) { exports = module.exports = LetterAvatar; } // But always support CommonJS module 1.1.1 spec (`exports` cannot be a function) exports.LetterAvatar = LetterAvatar; } else { window.LetterAvatar = LetterAvatar; d.addEventListener(&#39;DOMContentLoaded&#39;, function(event) { LetterAvatar.transform(); }); } })(window, document); </script>

原项目地址：https://github.com/daolavi/LetterAvatar

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