PHP がキャプション アバターを生成

if (!function_exists('letter_avatar')) {
    /**
     * 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" dominant-baseline="central">' . $first . '</text></svg>');
        $value = 'data:image/svg+xml;base64,' . $src;
        return $value;
    }
}

if (!function_exists('hsv2rgb')) {
    function hsv2rgb($h, $s, $v)
    {
        $r = $g = $b = 0;

        $i = floor($h * 6);
        $f = $h * 6 - $i;
        $p = $v * (1 - $s);
        $q = $v * (1 - $f * $s);
        $t = $v * (1 - (1 - $f) * $s);

        switch ($i % 6) {
            case 0:
                $r = $v;
                $g = $t;
                $b = $p;
                break;
            case 1:
                $r = $q;
                $g = $v;
                $b = $p;
                break;
            case 2:
                $r = $p;
                $g = $v;
                $b = $t;
                break;
            case 3:
                $r = $p;
                $g = $q;
                $b = $v;
                break;
            case 4:
                $r = $t;
                $g = $p;
                $b = $v;
                break;
            case 5:
                $r = $v;
                $g = $p;
                $b = $q;
                break;
        }

        return [
            floor($r * 255),
            floor($g * 255),
            floor($b * 255)
        ];
    }
}