用字母替代图片脚本:LetterAvatar(无插件实现)

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。

用字母替代图片脚本:LetterAvatar(无插件实现)-狐狸库

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:

function zm_gravatar_alt($altgravatar) {
 	if (have_comments()) {
 		$alt = get_comment_author();
 	}
 	else {
 		$alt = get_the_author_meta(\'display_name\');
 	}
 	$altgravatar= str_replace(\'alt=\'\'\', \'alt=\'\' . $alt . \'\' title=\'Gravatar for \' . $alt . \'\'\', $altgravatar); 	return $altgravatar; } add_filter(\'get_avatar\', \'zm_gravatar_alt\');

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。 展开收缩

另附LetterAvatar脚本演示代码:

<!DOCTYPE html>
<html>
	<h1>Letter Avatar</h1> <small><strong>用法:</strong></small> <pre> <code>&lt;img src=&quot;&quot; class=&quot;avatar photo&quot; width=&quot;256&quot; height=&quot;256&quot; alt=&quot;星空站长网&quot; color=&quot;#c40000&quot;&gt;</code> </pre> <img src=\"\" class=\"avatar photo\" height=\"240\" width=\"240\" alt=\"星空站长网\" color=\"#c40000\" /> <img src=\"\" class=\"avatar photo\" height=\"240\" width=\"240\" alt=\"站长\" color=\"#99CC66\" /> <img src=\"\" class=\"avatar photo\" height=\"240\" width=\"240\" alt=\"网\" color=\"#0D8ABC\" />
	<style>
		body {
			font-family: \"Helvetica Neue\", Helvetica, Arial, sans-serif;
		}
		
		pre {
			margin: 20px 0;
			padding: 20px;
			background: #fafafa;
		}
		
		.avatar {
			border-radius: 50%;
		}
	</style>
	<script src=\"https://libs.baidu.com/jquery/3.2.1/jquery.min.js \"></script>
	<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 || \'\';
					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(\' \'),
						initials, charIndex, colourIndex, canvas, context, dataURI;
					if(nameSplit.length == 1) {
						initials = nameSplit[0] ? nameSplit[0].charAt(0) : \'?\';
					} else {
						initials = nameSplit[0].charAt(0) + nameSplit[1].charAt(0);
					}
					if(w.devicePixelRatio) {
						size = (size * w.devicePixelRatio);
					}
					charIndex = (initials == \'?\' ? 72 : initials.charCodeAt(0)) - 64;
					colourIndex = charIndex % 20;
					canvas = d.createElement(\'canvas\');
					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(\'img[alt]\'), function(img, name, color) {
						name = img.getAttribute(\'alt\');
						color = img.getAttribute(\'color\');
						img.src = LetterAvatar(name, img.getAttribute(\'width\'), color);
						img.removeAttribute(\'avatar\');
						img.setAttribute(\'alt\', name);
					});
				}; // AMD support 		if (typeof define === \'function\' && define.amd) { 			 			define(function () { return LetterAvatar; }); 		 		// CommonJS and Node.js module support. 		} else if (typeof exports !== \'undefined\') { 			 			// Support Node.js specific `module.exports` (which can be a function) 			if (typeof module != \'undefined\' && 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(\'DOMContentLoaded\', function(event) { 				LetterAvatar.transform(); 			}); 		} 	})(window, document);
	</script>

</html>
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