<?php 

$im = ImageCreateFromJpeg("file.jpg"); 

$size = getimagesize("file.jpg"); 

$new = imagecreate($size[0], $size[1]); 

$black = imagecolorallocate($new, 0, 0, 0); 

$white = imagecolorallocate($new, 0xFF, 0xFF, 0xFF); 



for ($i = 1; $i < $size[0]; $i++) { 

for ($j = 1; $j < $size[1]; $j++) { 

$rgb = ImageColorAt($im, $i, $j); 

$r = ($rgb >> 16) & 0xFF; 

$g = ($rgb >>  & 0xFF; 

$b = $rgb & 0xFF; 

if ( $r < 128 && $r < 128 && $b < 128 ) { 

imagesetpixel($new, $i, $j, $black); 

} elseif ( $r >= 128 && $r >= 128 && $b >= 128 ) { 

imagesetpixel($new, $i, $j, $white); 

} 

} 

} 

header("Content-type: image/jpeg"); 

imagejpeg($new, null, 100); 

imagedestroy($im); 

imagedestroy($new); 

?>