php 生成以名字第一个字或首字母的图片

1. 参数为名字或者其他字符串
2. 返回html img标签的src的值，即图片地址。

/**
     * 首字母头像
     * @param $text
     * @return string
     */
    function letter_avatar($text)
    {
        $total = unpack('L', hash('adler32', $text, true))[1];
        $hue = $total % 360;
        list($r, $g, $b) = hsv2rgb($hue / 360, 0.3, 0.9);

        $bg = "rgb({$r},{$g},{$b})";
        $color = "#ffffff";
        $first = mb_strtoupper(mb_substr($text, 0, 1));
        $src = base64_encode('<svg xmlns="http://www.w3.org/2000/svg" version="1.1" height="100" width="100"><rect fill="' . $bg . '" x="0" y="0" width="100" height="100"></rect><text x="50" y="50" font-size="50" text-copy="fast" fill="' . $color . '" text-anchor="middle" text-rights="admin" alignment-baseline="central">' . $first . '</text></svg>');
        $value = 'data:image/svg+xml;base64,' . $src;
        return $value;
    }

引用方式：

<img src="data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZlcnNpb249IjEuMSIgaGVpZ2h0PSIxMDAiIHdpZHRoPSIxMDAiPjxyZWN0IGZpbGw9InJnYigxNjAsMjI5LDE5MikiIHg9IjAiIHk9IjAiIHdpZHRoPSIxMDAiIGhlaWdodD0iMTAwIj48L3JlY3Q+PHRleHQgeD0iNTAiIHk9IjUwIiBmb250LXNpemU9IjUwIiB0ZXh0LWNvcHk9ImZhc3QiIGZpbGw9IiNmZmZmZmYiIHRleHQtYW5jaG9yPSJtaWRkbGUiIHRleHQtcmlnaHRzPSJhZG1pbiIgYWxpZ25tZW50LWJhc2VsaW5lPSJjZW50cmFsIj5GPC90ZXh0Pjwvc3ZnPg==" style="width:30px;height:30px;border-radius:50%;" alt="">

其中src= “xxx” 的xxx部分就为函数返回的图片地址