Обработка больших изображений GD

function make_prev ($dir_file, $file_name, $w_pix, $h_pix, $type_res, $type_media, $remove) {
// превью

$output = '';
        if (!copy ($file_name,$dir_file)) $output = '';


        $up_pix_size = GetImageSize($dir_file);


$up_pix_resize1 = $up_pix_size[0];
$up_pix_resize2 = $up_pix_size[1];


    if ($up_pix_size[0]>=$up_pix_size[1]) {
        if ($up_pix_size[0] >= $w_pix) {
            $resize_k = $up_pix_size[0]/$up_pix_size[1];
            $up_pix_resize1 = $w_pix;
            $up_pix_resize2 = $up_pix_resize1 / $resize_k;
        }
    }
    if ($up_pix_size[0]<=$up_pix_size[1]) {
        if ($up_pix_size[1] >= $h_pix) {
            $resize_k = $up_pix_size[1]/$up_pix_size[0];
            $up_pix_resize2 = $h_pix;
            $up_pix_resize1 = $up_pix_resize2 / $resize_k;
        }

    }



$pix_up = 0;
$pix_left = 0;

if ($type_res==1) {
    $pix_up =  (($h_pix/2) - ($up_pix_resize2/2));
    $pix_left = (($w_pix/2) - ($up_pix_resize1/2));
    }

       
//echo (filetype($dir_file));

if (($type_media == 'jpeg') || ($type_media == 'jpg')) $up_pix_resize_in = ImageCreateFromjpeg ($dir_file);
if ($type_media == 'gif') $up_pix_resize_in = ImageCreateFromgif ($dir_file);
if ($type_media == 'png') $up_pix_resize_in = ImageCreateFrompng ($dir_file);

if ($type_res==1) { $up_pix_resize1_1 = $w_pix; $up_pix_resize2_2 = $h_pix; } else
{$up_pix_resize1_1 = $up_pix_resize1; $up_pix_resize2_2 = $up_pix_resize2; }

// создается новый файл, и задается его размер
        $up_pix_resize_out = imagecreatetruecolor($up_pix_resize1_1, $up_pix_resize2_2);
        $background = imagecolorallocate($up_pix_resize_out, 254, 254, 254);



// Копируем закаченное изображение, увеличив его
        ImageCopyResized ($up_pix_resize_out, $up_pix_resize_in, $pix_left, $pix_up, 0, 0, $up_pix_resize1, $up_pix_resize2, $up_pix_size[0], $up_pix_size[1] );

if ($remove==1) {
 unlink($dir_file);

 $dir_file = explode($type_media,$dir_file);

 $dir_file =  $dir_file[0].'jpg';
}

        imagejpeg ($up_pix_resize_out, $dir_file, 95);

        ImageDestroy($up_pix_resize_in);
        ImageDestroy($up_pix_resize_out);


    chmod($file_name, 0774);

//------------
$output = $dir_file;

return $output;

}