Captcha cracker php sample

<?php
echo "Leyendo imagen...\n";
$im = imagecreatefromjpeg("Captcha.jpg");
$out = imagecreatetruecolor(imagesx($im),imagesy($im));
echo "Limpiando...\n";
for($x=0;$x<imagesx($im);$x++){
    for($y=0;$y<imagesy($im);$y++){
        $pixel = imagecolorsforindex($im,(imagecolorat($im,$x,$y)));
        if($pixel['red']>=100 || $pixel['green']>=100 || $pixel['blue']>=100){
            $color=imagecolorexact($out,0,0,0);
            imagesetpixel($out,$x,$y,$color);
        }else{
            $color=imagecolorexact($out,255,255,255);
            imagesetpixel($out,$x,$y,$color);
        }
    }
}
echo "Finished!! Catpcha_cracked.png\n";
imagepng($out,"Captcha_cracked.png");
shell_exec("convert Captcha_cracked.png Captcha.pnm");
echo "Captcha_cracked: ";
echo shell_exec('gocr Captcha.pnm');
?>