Resizing images with PHP - loss of quality?

Hi, I'm using this code to resize images in 'main' directory and place them in 'tumb' directoy:

<?
$new_w = 200;
$cfg_fullsizepics_path = "main";
$cfg_thumb_path = "thumb";
$filepath = "main";
$dir = dir($filepath);
while($entry=$dir->read()) {
    if($entry == "." || $entry == "..") {
        continue;
    }
    $fp = @fopen("$filepath/$entry","r");
 $photo_filename = "$entry";
$image_stats = GetImageSize($cfg_fullsizepics_path."/".$entry);
$imagewidth = $image_stats[0];
$imageheight = $image_stats[1];
$img_type = $image_stats[2];
$ratio = ($imagewidth / $new_w);
$new_h = round($imageheight / $ratio);
if (!file_exists($cfg_thumb_path."/".$entry))  {
 if ($img_type=="2") {
 $src_img = imagecreatefromjpeg($cfg_fullsizepics_path."/".$entry);
 $dst_img = imagecreate($new_w,$new_h);
imagecopyresized($dst_img,$src_img,0,0,0,0,$new_w,$new_h,imagesx($src_img),imagesy($src_img));
imagejpeg($dst_img, "$cfg_thumb_path"."/$entry");
 } elseif  ($img_type=="3") {
 $dst_img=ImageCreate($new_w,$new_h);
 $src_img=ImageCreateFrompng($cfg_fullsizepics_path."/".$entry);
ImageCopyResized($dst_img,$src_img,0,0,0,0,$new_w,$new_h,ImageSX($src_img),ImageSY($src_img));
 Imagepng($dst_img, "$cfg_thumb_path"."/$entry");
 } elseif  ($img_type=="1") {
 $cfg_thumb_url=$cfg_fullsizepics_url;
 }
}
  echo "$entry";
  echo "
";
  }
?>

It works well, BUT the images that are resized come out with what looks like 256 colours with a blue tint. Can anyone tell me how to resize images but preserver the colour quality in php?

BTW, I can't use GD library as i don't have permissions to install it :(
thanks.