Location: PHPKode > scripts > Very Simple Captcha > very-simple-captcha/captcha.php
<?php

/* start sessions */
session_start();

class CaptchaSecurityImages {

  /* select the type of font, must be used in directoy in which script is being called into */
  var $font = 'Dungeon.ttf';

  function generateCode($characters) {
    $possible = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';
    $possible = $possible.$possible.'2345678923456789';
    $code = '';
    $i = 0;
    while ($i < $characters) { 
      $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
      $i++;
    }
    return $code;
  }

  function CaptchaSecurityImages($width = 145,$height = 35, $characters = 6) {
    $code = $this->generateCode($characters);
    $font_size = $height * 0.60;
    $image = @imagecreate($width, $height) or die('Cannot initialize new GD image stream');

    /* set the colours */
    $bgR = mt_rand(0, 255); $bgG = mt_rand(0, 255); $bgB = mt_rand(0, 255);
    $background_color = imagecolorallocate($image, $bgR, $bgG, $bgB);
    $noise_color = imagecolorallocate($image, abs(100 - $bgR), abs(100 - $bgG), abs(100 - $bgB));
    $text_color = imagecolorallocate($image, abs(255 - $bgR), abs(255 - $bgG), abs(255 - $bgB));

    /* generate random dots in background */
    for($i = 0; $i < ($width*$height) / 3; $i++) {
      imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
    }

    /* generate random lines in background */
    for($i = 0; $i < ($width*$height) / 150; $i++) {
      imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);
    }

    /* set random colors */
    $w = imagecolorallocate($image, abs(100 - $bgR), abs(100 - $bgG), abs(100 - $bgB));
    $r = imagecolorallocate($image, abs(100 - $bgR), abs(100 - $bgG), abs(100 - $bgB));

    /* Draw a dashed line, 5 red pixels, 5 white pixels */
    $style = array($r, $r, $r, $r, $r, $w, $w, $w, $w, $w);
    imagesetstyle($image, $style);
    imageline($image, 0, 0, $width, $height, IMG_COLOR_STYLED);
    imageline($image, $width, 0, 0, $height, IMG_COLOR_STYLED);

    /* create random polygon points */
    $values = array(
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),
        mt_rand(0, $width), mt_rand(0, $height),
        mt_rand(0, $height), mt_rand(0, $width),);

    /* create Random Colors then set it to $clr */
    $r = abs(100 - mt_rand(0, 255));
    $g = abs(100 - mt_rand(0, 255));
    $b = abs(100 - mt_rand(0, 255));
    $clr = imagecolorallocate($image, $r, $g, $b);

    /* create filled polygon with random points */
    imagefilledpolygon($image, $values, 6, $clr);

    /* set starting CenterX and CenterY
    $w = $width-($width/2);
    $h = $height-($height/2);

    /* create "bulls-eye" type ellipses
    imageellipse($image, ($width/2), ($height/2), $w, $h, $clr); $w -= 7; $h -= 7;
    imageellipse($image, ($width/2), ($height/2), $w, $h, $clr); $w -= 7; $h -= 7;
    imageellipse($image, ($width/2), ($height/2), $w, $h, $clr); $w -= 7; $h -= 7;
    imageellipse($image, ($width/2), ($height/2), $w, $h, $clr);

    /* create textbox and add text */
    $textbox = imagettfbbox($font_size, 0, $this->font, $code) or die('Error in imagettfbbox function');
    $x = ($width - $textbox[4])/2;
    $y = ($height - $textbox[5])/2;
    imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code) or die('Error in imagettftext function');

    /* pretty it */
    imageantialias($image, 100);
    imagealphablending($image, 1);
    imagelayereffect($image, IMG_EFFECT_OVERLAY);

    /* output captcha image to browser */
    header('Content-Type: image/jpeg');
    imagejpeg($image);
    imagedestroy($image);
    $_SESSION['key'] = $code;
  }
}

$captcha = new CaptchaSecurityImages(145, 35, rand(4, 6));

?>
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