PHP замена прозрачного фона в png на белый

<?php 
  function resize($file, $type = 1, $quality = 75, $tmp_path){ 
            $max_mini_size = 1000; 
            $max_size = 800; 
 
            if ($file['type'] == 'image/jpeg') $src = imagecreatefromjpeg ($file['tmp_name']); 
            else if ($file['type'] == 'image/png') $src = imagecreatefrompng ($file['tmp_name']); 
            else if ($file['type'] == 'image/gif') $src = imagecreatefromgif ($file['tmp_name']); 
            else return false; 
 
            $width_src = imagesx($src);  
            $height_src = imagesy($src); 
 
            if ($type == 1) 
                $width = $max_mini_size; 
            else if ($type == 2) 
                $width = $max_size; 
 
            if ($width_src < $width) { 
                $ratio       = $width_src/$width; 
                $width_dest  = round($width_src/$ratio); 
                $height_dest = round($height_src/$ratio); 
  
                $dest = imagecreatetruecolor($width_dest, $height_dest);         
 
                imagecopyresampled($dest, $src, 0, 0, 0, 0, $width_dest, $height_dest, $width_src, $height_src); 
 
                imagejpeg($src, $tmp_path . $file['name'], $quality); 
 
                imagedestroy($dest); 
                imagedestroy($src); 
                echo 'no'; 
 
                return $file['name']; 
            }else { 
                imagejpeg($src, $tmp_path . $file['name'], $quality); 
 
                imagedestroy($src); 
                 
                return $file['name']; 
            } 
?>

<?php 
  $white = imagecolorallocate($src, 255, 255, 255); 
  imagefill ($src, 0, 0, $white); 
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