Java raw image writer

<?php
//header('Content-Type: text/plain');
$fp=fopen('C:\Users\sebbu\Downloads\test.txt', 'r') or die('failed to open file');
$data=unpack('N', chr(0).fread($fp, 3));
$data=$data[1];
//var_dump($data);
$dim=unpack('n2', fread($fp, 4));
$width=$dim[1];
$height=$dim[2];
//var_dump($width, $height);
$img=imagecreatetruecolor($width, $height);
imageantialias($img, false);
imagealphablending($img, false);
$bg=imagecolorallocate($img, 255, 255, 255);
imagefill($img, 0, 0, $bg);
for($y=0;$y<$height;++$y) {
    for($x=0;$x<$width;++$x) {
        $pix=unpack('C3', fread($fp, 3));
        $red=$pix[1];
        $green=$pix[2];
        $blue=$pix[3];
        //var_dump($red, $green, $blue);
        //die();
        $col=imagecolorallocate($img, $red, $green, $blue);
        if($col === false) {
            echo 'imagecolorallocate failed for $red='.$red.' $green='.$green.' $blue='.$blue."\n";
            die();
        }
        imagesetpixel($img, $x, $y, $col);
    }
}
imagealphablending($img, true);
imagepng($img, 'C:\Users\sebbu\Downloads\test.png');
echo 'image created<br/>'."\n";
fclose($fp);
?>