SOURCE

/*
	 * 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[avatar]'), function(img, name, color) {
				name = img.getAttribute('avatar');
				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);

<h1>Letter Avatar(首字母头像)</h1>
<small><strong>Usage:</strong></small>
<p>默认(大小默认60x60,颜色随机,正方形)</p>
<pre>
<code>&lt;img avatar=&quot;Dao Lam&quot; &gt;</code>
</pre>
<p>指定宽高</p>
<pre>
<code>&lt;img width=&quot;100&quot; height=&quot;100&quot; avatar=&quot;Dao Lam&quot; &gt;</code>
</pre>
<p>指定颜色</p>
<pre>
<code>&lt;img width=&quot;100&quot; height=&quot;100&quot; avatar=&quot;Dao Lam&quot; color=&quot;#0D8ABC&quot;&gt;</code>
</pre>
<p>指定圆角</p>
<pre>
<code>&lt;img class=&quot;round&quot; width=&quot;100&quot; height=&quot;100&quot; avatar=&quot;Dao Lam&quot; color=&quot;#0D8ABC&quot;&gt;</code>
</pre>

<div>
  <img avatar="P">
</div>
<br>
<div>
  <img width="100" height="100" avatar="P">
  <img width="100" height="100" avatar="H">
  <img width="100" height="100" avatar="P" color="#2c3e50">
  <img width="100" height="100" avatar="演示">
</div>
<br>
<div>
  <img class="round" width="100" height="100" avatar="圆">
  <img class="round" width="100" height="100" avatar="角">
  <img class="round" width="100" height="100" avatar="示" color="#e67e22">
  <img class="round" width="100" height="100" avatar="例" color="#1abc9c">
</div>
<br>
<div>
  <img width="100" height="100" avatar="Dao Lam">
  <img class="round" width="100" height="100" avatar="Dao Lam">
</div>

body {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
}

pre {
  margin: 20px 0;
  padding: 20px;
  background: #fafafa;
}

.round {
  border-radius: 50%;
}