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<?php
/**
* Creates a CAPTCHA image
*
* @author Stefan Gabos <[email protected]>
* @copyright (c) 2006 - 2008 Stefan Gabos
*/
// as this file actually generates an image we set the headers accordingly
//header('Content-type:image/jpeg');
// the number of characters to be used in the generated image
$charactersNumber = 5;
// spacing between characters (this can also be a negative number)
// you should leave this as it is (unless you want to increase it)
// decreasing this value may result in characters overlapping and being hardly distinguishable
$characterSpacing = -2;
// each character's size will be randomly selected from this range
$fontSizeVariation = array(20, 40);
// each character's angle will be randomly selected from this range
// (remember to also change the character spacing if you change these to avoid character overlapping)
$fontAngleVariation = array(-10, 10);
// the number of horizontal lines to be drawn on the generated image
$linesNumber = 15;
// if you changed anything above, you should probably change this too si that all the characters fit into the image
// and there's not too much of blank space
$imageWidth = 140;
// if you changed anything above, you should probably change this too si that all the characters fit into the image
// and there's not too much of blank space
$imageHeight = 50;
// the quality, in percents, of the generated image
$imageQuality = 70;
// list of characters from which to choose
// (notice that characters that can be (in some circumstances) confused with others, are missing)
// you should not alter this setting
$charList = 'bcdkmpsx345678';
$captcha = array();
$resultString = '';
$totalWidth = 0;
// this is the used font
$font = 'babelsans-bold.ttf';
// first we figure out how much space the character would take
for ($i = 0; $i < $charactersNumber; $i++) {
// get a random character
$char = $charList[rand(0, strlen($charList) - 1)];
$resultString .= $char;
// get a random size for the character
$charSize = rand($fontSizeVariation[0], $fontSizeVariation[1]);
// get a random angle for the character
$charAngle = rand($fontAngleVariation[0], $fontAngleVariation[1]);
// get the bounding box of the character
$bbox = imagettfbbox($charSize, $charAngle, $font, $char);
// resolve the returned measurements
$bbox['left'] = abs(min($bbox[0], $bbox[2], $bbox[4], $bbox[6]));
$bbox['top'] = abs(min($bbox[1], $bbox[3], $bbox[5], $bbox[7]));
$bbox['width'] = max($bbox[0], $bbox[2], $bbox[4], $bbox[6]) - min($bbox[0], $bbox[2], $bbox[4], $bbox[6]);
$bbox['height'] = max($bbox[1], $bbox[3], $bbox[5], $bbox[7]) - min($bbox[1], $bbox[3], $bbox[5], $bbox[7]);
// this will be the total width of the random generated word
$totalWidth += $bbox['width'] + $characterSpacing;
// save info about the current character
$captcha[] = array(
'char' => $char,
'size' => $charSize,
'angle' => $charAngle,
'box' => $bbox
);
}
// sets a cookie that will later be read by the form generator and used to see if user entered the correct characters
setcookie('captcha', md5(md5(md5($resultString))), time() + 3600, '/');
// create the image
$img = imagecreatetruecolor($imageWidth, $imageHeight);
// allocate some colors
$white = imagecolorallocate($img, 255, 255, 255);
$black = imagecolorallocate($img, 0, 0, 0);
// fill the canvas to white
imagefilledrectangle($img, 0, 0, $imageWidth, $imageHeight, $white);
// draw a bounding rectangle
imagerectangle($img, 0, 0, $imageWidth - 1, $imageHeight - 1, $black);
// this is to keep the word centered in the box
$left = (($imageWidth - $totalWidth) / 2);
// iterate through the chosen characters
foreach ($captcha as $values) {
// print each character
imagettftext($img, $values['size'], $values['angle'], $left , ($imageHeight + $values['box']['height']) / 2 , $black, $font, $values['char']);
// compute the position of the next character
$left += $values['box']['width'] + $characterSpacing;
}
$lines = array();
// start drawing the number of lines specified in $linesNumber
for ($i = 0; $i < $linesNumber; $i++) {
// get a random position for the line (inside the box so that we don't write on the margins)
$line = rand(2, $imageHeight - 2);
$counter = 0;
// if the line is not allowed at that position
// and we've not reached $imageHeight iterations (this is to ensure we don't get infinite loops)
while (in_array($line, $lines) && ++$counter < $imageHeight) {
// pick a new random position
$line = rand(2, $imageHeight - 2);
}
// save the position of the line
$lines[] = $line;
// and also save adjacent positions so that lines are not drawn near each other but having at least one pixel between
$lines[] = $line - 1;
$lines[] = $line + 1;
// draw the line using white color
imageline($img, 1, $line, $imageWidth - 2, $line, $white);
}
// and finally output the image at the specified quality
imagejpeg($img, '', $imageQuality);
// free memory
imagedestroy($img);
?>
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