Problema .PNG resizing

[the blader]

Ciao Alhazred! Scusa, hai ragione, ora dovrebbe essere meglio:

$allowed_type = array("image/jpeg","image/pjpeg", "image/gif", "image/x-png", "image/png");
    $type = $_FILES["image_upload_box"]["type"];
    
    
            // get width and height of original image
    list($image_width, $image_height) = getimagesize($_FILES["image_upload_box"]["tmp_name"]);
 
$OS = $_POST['OS'];
$pub_name = $_POST['pub_name'];
$lang = $_POST['lang'];








    // file needs to be jpg,gif,bmp,x-png, 4 MB max and width 320,640.
    if (in_array($type, $allowed_type) && ($_FILES["image_upload_box"]["size"] < 4000000) && ($image_width == 640) && ($image_height == 100)) {


  


        
        // if uploaded image was JPG/JPEG
        if($_FILES["image_upload_box"]["type"] == "image/jpeg" || $_FILES["image_upload_box"]["type"] == "image/pjpeg"){    
            $image_source = imagecreatefromjpeg($_FILES["image_upload_box"]["tmp_name"]);
        }        
        // if uploaded image was GIF
        if($_FILES["image_upload_box"]["type"] == "image/gif"){    
            $image_source = imagecreatefromgif($_FILES["image_upload_box"]["tmp_name"]);
        }    
        // BMP doesn't seem to be supported so remove it form above image type test (reject bmps)    
        // if uploaded image was BMP
        if($_FILES["image_upload_box"]["type"] == "image/bmp"){    
            $image_source = imagecreatefromwbmp($_FILES["image_upload_box"]["tmp_name"]);
        }            
        // if uploaded image was PNG
        if($_FILES["image_upload_box"]["type"] == "image/png" || $_FILES["image_upload_box"]["type"] == "image/x-png"){
            $image_source = imagecreatefrompng($_FILES["image_upload_box"]["tmp_name"]);
        }
        


    
        
        $remote_file = "image_files/".rand(0,10000).$_FILES["image_upload_box"]["name"];
        imagejpeg($image_source,$remote_file,100);
        chmod($remote_file,0644);
    
    


    
        
            
            $new_width = 320;
            $new_height = 50;
            
            
            $new_image = imagecreatetruecolor($new_width , $new_height);
            $image_source = imagecreatefromjpeg($remote_file);
            


            
            imagecopyresampled($new_image, $image_source, 0, 0, 0, 0, $new_width, $new_height, $image_width, $image_height);
            imagejpeg($new_image,$remote_file,100);
            
            imagedestroy($new_image);
                
        imagedestroy($image_source);
        
        //final file name
        $resized_name = basename($remote_file); 

Ho trovato alcune soluzioni, tipo imagesavealpha(), ma non so in che parte del codice dovrei inserirla.
Il problema persiste solo con le immagini trasparenti, ma la maggiore utilità dello script dovrebbe essere proprio con queste ultime. Qualche idea?