Download then open image on IOS

This code works perfectly on Android, but won`t do anything on IOS:

 public class OnPressingPictureButton : MonoBehaviour {
 
     public int currentPage;
     public string [] imageURL;
     public Book book;
 
     public GameObject loading;
 
 
 // Update is called once per frame
     void Update () {
 
         currentPage = book.page;
 
 }
 
 
 void OnMouseDown ()
     {
         loading.SetActive (true); //@@@ "Loading ON"
 
 
         //Checking if the file exists in the users device
         if (System.IO.File.Exists (Application.persistentDataPath + "/image" + currentPage.ToString() + ".jpg")) {
             //if yes, open it
             loading.SetActive (false);
             Application.OpenURL (Application.persistentDataPath + "/image" + currentPage.ToString() + ".jpg");
         } 
 
 
 
 
         //if not, download it
         else {
             StartCoroutine (TestDownload (imageURL [currentPage]));
         }
     }
 
 
     private IEnumerator TestDownload (string uRL)
     {
 
         WWW www = new WWW (uRL);
         yield return www;
 
         while (!www.isDone) {
 
             Debug.Log (www.progress);
             yield return null;
         }
 
 
         string savePath = Application.persistentDataPath + "/image" + currentPage.ToString() + ".jpg";
 
         byte[] bytes = www.bytes;
 
         System.IO.File.WriteAllBytes (savePath, bytes);
 
         loading.SetActive (false); //@@@ "Loading OFF"
 
         Application.OpenURL (savePath);
 
     }
 }

I tried changing from "File.Exists" to "Directory.Exists" and also added "file://" on the beginning of savePath variable, but it still does not seem to work.

any ideas?