Captcha 2.0

<?php
    function make_text($img, $c = 5){
        $txt = "";
        $arr = array();
        for($i = 0; $i < $c; $i++){
            switch(mt_rand(0,2)){
                case(0):
                    $txt.=mt_rand(0,9);
                    break;
                case(1):
                    $txt.=chr(ord('a')+mt_rand(0,25));
                    break;
                case(2):
                    $txt.=chr(ord('A')+mt_rand(0,25));
                    break;
            }
            $arr[] = $i;
        }
        shuffle($arr);
        $sx = ImageSX($img);
        $sy = ImageSY($img);
        $wm = 0;
        foreach($arr as $i){
            $s = mt_rand($sy/2,$sy/3*2);
            $a = mt_rand(-20,20);
            $f = "font".mt_rand(1,6).".ttf";
            $b = ImageTtfBBox($s,$a,$f,$txt[$i]);
            $h = max($b[1]-$b[7],$b[3]-$b[5]);
            $x = $i*$sx/$c-(($a>0)?$b[6]:0);
            $y = mt_rand($h,max($h,$sy-($a<0?$b[3]:$b[1])));
            $cl = ImageColorAllocateAlpha($img,0,0,0,64);
            ImageTtfText($img,$s,$a,$x,$y,$cl,$f,$txt[$i]);
            $x-=mt_rand(1,3);$y-=mt_rand(1,3);
            $cl = ImageColorAllocateAlpha($img,255,255,255,56);
            ImageTtfText($img,$s,$a,$x,$y,$cl,$f,$txt[$i]);
        }
        return $txt;
    }
    function make_wave($img){
        $x = ImageSX($img);
        $y = ImageSY($img);
        $c = array();
        $r = mt_rand(0,255);
        $g = mt_rand(0,255);
        $b = mt_rand(0,255);
        $j = mt_rand(5,10);
        for($i = 0; $i < $j; $i++)
            $c[] = ImageColorAllocateAlpha($img,$r,$g,$b,($i/$j*127));
        $start = mt_rand(0,$y);
        $angle = mt_rand(-90,90);
        for($i = 0; $i < $x; $i++){
            $sine = sin($i/$j)*$j+($angle*$i/$y);
            ImageSetPixel($img,$i,round(($start+$sine)%$y),$c[0]);
            for($j = 1; $j < count($c); $j++){
                ImageSetPixel($img,$i,round(($start+$sine-$j)%$y),$c[$j]);
                ImageSetPixel($img,$i,round(($start+$sine+$j)%$y),$c[$j]);
            }
        }
    }
    function make_bg($img){
        $x = ImageSX($img);
        $y = ImageSY($img);
        $bg = ImageCreateTrueColor($x,$y);
        imageSaveAlpha($bg, true);
        imageAlphaBlending($bg, true);
        $c = ImageColorAllocate($bg,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
        ImageFilledRectangle($bg,0,0,$x,$y,$c);
        $c=mt_rand(8,10);
        for($i=0;$i<$c;$i++){
            make_wave($bg);
        }
        ImageCopy($img,$bg,0,0,0,0,$x,$y);
        ImageDestroy($bg);
    }
    $img = ImageCreateTrueColor(200,60);
    imageSaveAlpha($img, true);
    imageAlphaBlending($img, true);
    make_bg($img);
    $text = make_text($img);
    ob_start();
    ImagePng($img);
    ImageDestroy($img);
    $img = "data:image/png;base64,".base64_encode(ob_get_contents());
    ob_end_clean();
    echo "<img src=\"".$img."\" alt=\"captcha\"/>";