偶然发现码云上有个非常人性化的细节：会自动给没头像的用户生成一个昵称首字符的彩色头像

实现纯前端生成字母头像

偶然发现码云上有个非常人性化的细节：会自动给没头像的用户生成一个昵称首字符的彩色头像，关键是打开控制台一看，发现这头像居然还是在前端实时生成的 这就很有意思了！ !....

发现这头像居然还是在前端实时生成的 这就很有意思了！

它使用的是一个叫 LetterAvatar 的 JS 插件。它的原理是利用动态创建的 canvas 生成图像，然后显示在 img 标签中。

JS代码：

/**
 * 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 || 80;
        var colours = [
                "#1abc9c", "#2ecc71", "#3498db", "#9b59b6", "#34495e", "#16a085", "#27ae60", "#2980b9", "#8e44ad", "#2c3e50", 
                "#f1c40f", "#e67e22", "#e74c3c", "#00bcd4", "#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 'Microsoft Yahei'";
        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);

把这段代码放到自己的主题js里面就可以了，然后再修改主题的头像功能，比如我这边的是

/* 解析头像 */
function getGravatar($mail)
{
    $a = Typecho_Widget::widget('Widget_Options')->JGravatars;
    $b = 'https://' . $a . '/';
    $c = strtolower($mail); //转为小写
    $d = md5($c);
    $f = str_replace('@qq.com', '', $c);
    if (strstr($c, "qq.com") && is_numeric($f) && strlen($f) < 11 && strlen($f) > 4) {
        $g = '//thirdqq.qlogo.cn/g?b=qq&nk=' . $f . '&s=100';
    } else {
        //$g = $b . $d . '?d=mm';
        $g = '-1'; //不再输出Gravatar的头像，换成Letter Avatar头像
    }
    return $g; 
}

以上是如果为正常的qq邮箱，则输出qq头像，如果不是qq邮箱，则输出$g=-1

然后再经过这一段

function get_tx($mail){
    $tx = getGravatar($mail);
    $name = get_name($mail);
    if($tx=='-1'){
        return '<img class="flex-avatar me-3" avatar="'.$name.'">'; //Letter Avatar头像
    }
    else{
        return '<img src="'.$tx.'" srcset="'.$tx.'" class="avatar">';
    }
}

判断是否为$g=-1，-1的时候则显示Letter Avatar头像，否则显示QQ邮箱头像

以上的getGravatar获取qq头像，get_name获取用户昵称

最后

前端调用头像代码：

<?php echo get_tx($this->author->mail); ?>