[PHP] Jak wygenerować miniaturkę z pliku PNG? Opcje

[pehaperowiec]

Napisałem taki kod do generowania miniaturek z pliku jpg, gif oraz png

[PHP] pobierz, plaintext 
<?php
 
if(isset($_FILES['img_main']['tmp_name']) && is_uploaded_file($_FILES['img_main']['tmp_name'])) {
	if($_FILES['img_main']['type']=="image/png" || $_FILES['img_main']['type']=="image/jpeg" || $_FILES['img_main']['type']=="image/gif") {
		move_uploaded_file($_FILES['img_main']['tmp_name'], "../gal/".$tab['gallery_name']."/".$_FILES['img_main']['name']);
 
		$img_path="../gal/".$tab['gallery_name']."/".$_FILES['img_main']['name'];
		$thumb_path="../gal/".$tab['gallery_name']."/thumbs/".$_FILES['img_main']['name'];
		$max_width=$max_height=100;
		$img_attr = getimagesize($img_path);
		if($img_attr[0]>$img_attr[1]){
			 $scale = $img_attr[0] / $max_width;
		 }else{
			 $scale = $img_attr[1] / $max_height;
		 }
		 $w = floor($img_attr[0]/$scale);
		 $h = floor($img_attr[1]/$scale);
		 $thumb = imagecreatetruecolor($w,$h);
		 switch($_FILES['img_main']['type']) {
			case "image/jpeg": {
				imagecopyresampled($thumb, imagecreatefromjpeg($img_path), 0, 0, 0, 0, $w, $h, $img_attr[0], $img_attr[1]);
				imagejpeg($thumb,$thumb_path,85);
				break;
			}
			case "image/png": {
				imagecopyresampled($thumb, imagecreatefrompng($img_path), 0, 0, 0, 0, $w, $h, $img_attr[0], $img_attr[1]);
				//header('Content-type: image/png');
				imagepng($thumb,$thumb_path,85);
			        break;
			}
			case "image/gif": {
				imagecopyresampled($thumb, imagecreatefromgif($img_path), 0, 0, 0, 0, $w, $h, $img_attr[0], $img_attr[1]);
				imagegif($thumb,$thumb_path,85);
				break;
			}
		 }
	} 				
}
 
?>
[PHP] pobierz, plaintext 

Jednak przy próbie generacji miniaturki PNG zwraca błąd:

Kod

Warning: imagepng() [function.imagepng]: gd-png error: compression level must be 0 through 9 in D:\wamp\www\class\class_admin.php on line 289

Linia 289 to:

[PHP] pobierz, plaintext 
imagepng($thumb,$thumb_path,85);
[PHP] pobierz, plaintext 

Dodatkowo WampSerwer się "wykrzacza" podczas tej operacji. Czy ktoś ma na to jakiś pomysł?