<?php
function convertJPEGtoMonochromeGIF( $infile, $outfile ) {
        list($width, $height) = getimagesize($infile);
        $source = imagecreatefromjpeg($infile);
        $bwimage= imagecreate($width, $height);

        $paletteBlack = imagecolorallocate( $bwimage, 0, 0, 0 );
        $paletteWhite = imagecolorallocate( $bwimage, 255, 255, 255 );

        for ($y=0;$y<$height;$y++)
        for ($x=0;$x<$width;$x++)
        {
                $rgb = imagecolorat($source,$x,$y);
                $r = ($rgb >> 16) & 0xFF;
                $g = ($rgb >> 8) & 0xFF;
                $b = $rgb & 0xFF;

                $gs = (($r*0.299)+($g*0.587)+($b*0.114));
                if ( $gs > 150 )
                        imagesetpixel($bwimage,$x,$y,$paletteWhite);
                else
                        imagesetpixel($bwimage,$x,$y,$paletteBlack);
        }
        imagegif( $bwimage, $outfile );
}

?>