captcha.class.php

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<?php
class captcha {

        private $_name;

        private $_width;
        
        private $_height;

        private $_font_file;
        
        private $_letters;

        private $_numbers;

        private $_allow_numbers;

        function __construct($name, $opts=null) {

                $this->_name = $name;
                $this->_width = 200;
                $this->_height = 40;

                $this->_font_file = ABS_ROOT.DS.'font'.DS.'initial.ttf';

                $this->_letters = array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z");
                $this->_numbers = array("0", "1", "2", "3", "4", "5", "6", "7", "8", "9");

                $this->_allow_numbers = gOpt($opts, 'allow_numbers', false);;
        
        }

        public function render($opts=null) {
        
                $bkg_color = gOpt($opts, "bkg_color", "#00ff00");
                $color = gOpt($opts, "color", "#000000");

                $image = ImageCreatetruecolor($this->_width, $this->_height);

                // background
                $bcs = $this->hex2RGB($bkg_color);
                $bkg_c = ImageColorAllocate($image, $bcs['red'], $bcs['green'], $bcs['blue']);
                imagefill($image, 0, 0, $bkg_c);

                // text
                $tcs = $this->hex2RGB($color);
                $text_c = ImageColorAllocate($image, $tcs['red'], $tcs['green'], $tcs['blue']);
                list($s1, $s2) = $this->generateStrings();
                imagettftext($image, 22, 2, 5, $this->_height-5, ImageColorAllocate($image, 0, 0, 0), $this->_font_file, $s1);
                imagettftext($image, 22, -5, 110, 25, ImageColorAllocate($image, 0, 0, 0), $this->_font_file, $s2);

                // ellipses
                $i = 0;
                while($i<$this->_width-5) {
                        $ell_color = ImageColorAllocate($image, rand(0,255), rand(0,255), rand(0,255));
                        imagefilledellipse($image , $i+5 , rand(5, $this->_height-5) , rand(0, 8) , rand(0, 8), $ell_color);
                        $i = $i+20;
                }

                // lines
                $i = 0;
                while($i<$this->_width-3) {
                        $line_color = ImageColorAllocate($image, rand(0,255), rand(0,255), rand(0,255));
                        imagesetthickness($image, rand(0,2));
                        imageline($image, $i , rand(0, $this->_height) , rand($i, $i+20) , rand(0, $this->_height) , $line_color);
                        $i = $i+10;
                }

                ob_start();
                imagejpeg($image);
                imagedestroy($image);
                $img = ob_get_contents();
                ob_end_clean();

                $_SESSION['captcha_code'] = $s1.$s2;

                $buffer = "<img src=\"data:image/jpeg;base64,".base64_encode($img)."\" /><br />";
                $buffer .= "<input name=\"$this->_name\" type=\"text\" size=\"10\" maxlength=\"20\" required=\"required\" />";

                return $buffer;

        }

        private function generateStrings() {
        
                $s1 = $s2 = '';

                $coin = rand(0,10) < 5 ? true : false;
                
                $ls1 = $coin ? 5 : 4;
                $ls2 = $coin ? 4 : 5;

                for($i=0; $i<$ls1; $i++) { 
                        $coin = $this->_allow_numbers ? rand(0, 10) : 0;
                        $s1 .= $coin < 5 ? $this->_letters[array_rand($this->_letters)] : $this->_numbers[array_rand($this->_numbers)];
                }

                for($i=0; $i<$ls2; $i++) { 
                        $coin = $this->_allow_numbers ? rand(0, 10) : 0;
                        $s2 .= $coin < 5 ? $this->_letters[array_rand($this->_letters)] : $this->_numbers[array_rand($this->_numbers)];
                }

                return array($s1, $s2);

        }

        private function hex2RGB($hexStr) {
    
                $hexStr = preg_replace("/[^0-9A-Fa-f]/", '', $hexStr); // Gets a proper hex string
                $rgbArray = array();
    
                if (strlen($hexStr) == 6) { //If a proper hex code, convert using bitwise operation. No overhead... faster
                        $colorVal = hexdec($hexStr);
                        $rgbArray['red'] = 0xFF & ($colorVal >> 0x10);
                        $rgbArray['green'] = 0xFF & ($colorVal >> 0x8);
                        $rgbArray['blue'] = 0xFF & $colorVal;
                } 
                elseif (strlen($hexStr) == 3) { //if shorthand notation, need some string manipulations
                        $rgbArray['red'] = hexdec(str_repeat(substr($hexStr, 0, 1), 2));
                        $rgbArray['green'] = hexdec(str_repeat(substr($hexStr, 1, 1), 2));
                        $rgbArray['blue'] = hexdec(str_repeat(substr($hexStr, 2, 1), 2));
                } 
                else {
                        return false; //Invalid hex color code
    
                }
    
                return $rgbArray; // returns the rgb string or the associative array
        }

        public function check() {
        
                $string = preg_replace("#[ \s]#", "", $_POST[$this->_name]);

                if(!$string) return false;

                $result = $string === $_SESSION['captcha_code'] ? true : false;

                unset($_SESSION['captcha_code']);

                return $result;

        } 

}

?>