<?php

class KCAPTCHA{

    // generates keystring and image
    function KCAPTCHA(){

        $alphabet = "0123456789abcdefghijklmnopqrstuvwxyz"; # do not change without changing font files!

        # symbols used to draw CAPTCHA
        //$allowed_symbols = "0123456789"; #digits
        $allowed_symbols = "23456789abcdeghkmnpqsuvxyz"; #alphabet without similar symbols (o=0, 1=l, i=j, t=f)

        # folder with fonts
        $fontsdir = 'fonts';    

        # CAPTCHA string length
        $length = mt_rand(5,6); # random 5 or 6
        //$length = 6;

        # CAPTCHA image size (you do not need to change it, whis parameters is optimal)
        $width = 100;
        $height = 50;

        # symbol's vertical fluctuation amplitude divided by 2
        $fluctuation_amplitude = 5;

        # increase safety by prevention of spaces between symbols
        $no_spaces = false;

        # show credits
        $show_credits = false; # set to false to remove credits line. Credits adds 12 pixels to image height

        # CAPTCHA image colors (RGB, 0-255)
        $foreground_color = array(0, 0, 0);
        $background_color = array(250, 250, 250);
        //$foreground_color = array(mt_rand(0,100), mt_rand(0,100), mt_rand(0,100));
        //$background_color = array(mt_rand(200,255), mt_rand(200,255), mt_rand(200,255));

        # JPEG quality of CAPTCHA image (bigger is better quality, but larger file size)
        $jpeg_quality = 90;

        $fonts=array();
        $fontsdir_absolute=dirname(__FILE__).'/'.$fontsdir;
        if ($handle = opendir($fontsdir_absolute)) {
            while (false !== ($file = readdir($handle))) {
                if (preg_match('/\.png$/i', $file)) {
                    $fonts[]=$fontsdir_absolute.'/'.$file;
                }
            }
            closedir($handle);
        }   

        $alphabet_length=strlen($alphabet);
        
        while(true){
            // generating random keystring
            while(true){
                $this->keystring='';
                for($i=0;$i<$length;$i++){
                    $this->keystring.=$allowed_symbols{mt_rand(0,strlen($allowed_symbols)-1)};
                }
                if(!preg_match('/cp|cb|ck|c6|c9|rn|rm|mm|co|do|cl|db|qp|qb|dp/', $this->keystring)) break;
            }
        
            $font_file=$fonts[mt_rand(0, count($fonts)-1)];
            $font=imagecreatefrompng($font_file);
            imagealphablending($font, true);
            $fontfile_width=imagesx($font);
            $fontfile_height=imagesy($font)-1;
            $font_metrics=array();
            $symbol=0;
            $reading_symbol=false;

            // loading font
            for($i=0;$i<$fontfile_width && $symbol<$alphabet_length;$i++){
                $transparent = (imagecolorat($font, $i, 0) >> 24) == 127;

                if(!$reading_symbol && !$transparent){
                    $font_metrics[$alphabet{$symbol}]=array('start'=>$i);
                    $reading_symbol=true;
                    continue;
                }

                if($reading_symbol && $transparent){
                    $font_metrics[$alphabet{$symbol}]['end']=$i;
                    $reading_symbol=false;
                    $symbol++;
                    continue;
                }
            }

            $img=imagecreatetruecolor($width, $height);
            imagealphablending($img, true);
            $white=imagecolorallocate($img, 255, 255, 255);
            $black=imagecolorallocate($img, 0, 0, 0);

            imagefilledrectangle($img, 0, 0, $width-1, $height-1, $white);

            // draw text
            $x=1;
            for($i=0;$i<$length;$i++){
                $m=$font_metrics[$this->keystring{$i}];

                $y=mt_rand(-$fluctuation_amplitude, $fluctuation_amplitude)+($height-$fontfile_height)/2+2;

                if($no_spaces){
                    $shift=0;
                    if($i>0){
                        $shift=1000;
                        for($sy=7;$sy<$fontfile_height-20;$sy+=1){
                            //for($sx=$m['start']-1;$sx<$m['end'];$sx+=1){
                            for($sx=$m['start']-1;$sx<$m['end'];$sx+=1){
                                $rgb=imagecolorat($font, $sx, $sy);
                                $opacity=$rgb>>24;
                                if($opacity<127){
                                    $left=$sx-$m['start']+$x;
                                    $py=$sy+$y;
                                    if($py>$height) break;
                                    for($px=min($left,$width-1);$px>$left-12 && $px>=0;$px-=1){
                                        $color=imagecolorat($img, $px, $py) & 0xff;
                                        if($color+$opacity<190){
                                            if($shift>$left-$px){
                                                $shift=$left-$px;
                                            }
                                            break;
                                        }
                                    }
                                    break;
                                }
                            }
                        }
                        if($shift==1000){
                            $shift=mt_rand(4,6);
                        }

                    }
                }else{
                    $shift=1;
                }
                imagecopy($img,$font,$x-$shift,$y,$m['start'],1,$m['end']-$m['start'],$fontfile_height);
                $x+=$m['end']-$m['start']-$shift;
            }
            if($x<$width-10) break; // fit in canvas
            
        }
        $center=$x/2;

        // credits. To remove, see configuration file
        $img2=imagecreatetruecolor($width, $height+($show_credits?12:0));
        $foreground=imagecolorallocate($img2, $foreground_color[0], $foreground_color[1], $foreground_color[2]);
        $background=imagecolorallocate($img2, $background_color[0], $background_color[1], $background_color[2]);
        imagefilledrectangle($img2, 0, $height, $width-1, $height+12, $foreground);
        $credits=empty($credits)?$_SERVER['HTTP_HOST']:$credits;
        imagestring($img2, 2, $width/2-ImageFontWidth(2)*strlen($credits)/2, $height-2, $credits, $background);

        // periods
        $rand1=mt_rand(750000,1200000)/10000000;
        $rand2=mt_rand(750000,1200000)/10000000;
        $rand3=mt_rand(750000,1200000)/10000000;
        $rand4=mt_rand(750000,1200000)/10000000;
        // phases
        $rand5=mt_rand(0,3141592)/500000;
        $rand6=mt_rand(0,3141592)/500000;
        $rand7=mt_rand(0,3141592)/500000;
        $rand8=mt_rand(0,3141592)/500000;
        // amplitudes
        $rand9=mt_rand(330,420)/110;
        $rand10=mt_rand(330,450)/110;

        //wave distortion
        for($x=0;$x<$width;$x++){
            for($y=0;$y<$height;$y++){
                $sx=$x+(sin($x*$rand1+$rand5)+sin($y*$rand3+$rand6))*$rand9-$width/2+$center+1;
                $sy=$y+(sin($x*$rand2+$rand7)+sin($y*$rand4+$rand8))*$rand10;

                if($sx<0 || $sy<0 || $sx>=$width-1 || $sy>=$height-1){
                    $color=255;
                    $color_x=255;
                    $color_y=255;
                    $color_xy=255;
                }else{
                    $color=imagecolorat($img, $sx, $sy) & 0xFF;
                    $color_x=imagecolorat($img, $sx+1, $sy) & 0xFF;
                    $color_y=imagecolorat($img, $sx, $sy+1) & 0xFF;
                    $color_xy=imagecolorat($img, $sx+1, $sy+1) & 0xFF;
                }

                if($color==0 && $color_x==0 && $color_y==0 && $color_xy==0){
                    $newred=$foreground_color[0];
                    $newgreen=$foreground_color[1];
                    $newblue=$foreground_color[2];
                }else if($color==255 && $color_x==255 && $color_y==255 && $color_xy==255){
                    $newred=$background_color[0];
                    $newgreen=$background_color[1];
                    $newblue=$background_color[2];  
                }else{
                    $frsx=$sx-floor($sx);
                    $frsy=$sy-floor($sy);
                    $frsx1=1-$frsx;
                    $frsy1=1-$frsy;

                    $newcolor=(
                        $color*$frsx1*$frsy1+
                        $color_x*$frsx*$frsy1+
                        $color_y*$frsx1*$frsy+
                        $color_xy*$frsx*$frsy);

                    if($newcolor>255) $newcolor=255;
                    $newcolor=$newcolor/255;
                    $newcolor0=1-$newcolor;

                    $newred=$newcolor0*$foreground_color[0]+$newcolor*$background_color[0];
                    $newgreen=$newcolor0*$foreground_color[1]+$newcolor*$background_color[1];
                    $newblue=$newcolor0*$foreground_color[2]+$newcolor*$background_color[2];
                }

                imagesetpixel($img2, $x, $y, imagecolorallocate($img2, $newred, $newgreen, $newblue));
            }
        }

        if(function_exists("imagejpeg")){
            header("Content-Type: image/jpeg");
            imagejpeg($img2, null, $jpeg_quality);
        }else if(function_exists("imagegif")){
            header("Content-Type: image/gif");
            imagegif($img2);
        }else if(function_exists("imagepng")){
            header("Content-Type: image/x-png");
            imagepng($img2);
        }
    }

    // returns keystring
    function getKeyString(){
        return $this->keystring;
    }
}

?>
