Download Image to a new album (Android)

I have a button that saves an image from URL to the device, and then opens it. I want all the images to save in a new abloum which will be created when pressing the button. current code is:

 using UnityEngine;
 using System.Collections;
 
 public class OnPressingPictureButton : MonoBehaviour {
 
     public int currentPage;
     public string [] imageURL;
     public Book book;
 
 // Update is called once per frame
     void Update () {
 
         currentPage = book.page;
 
 }
 
 
 void OnMouseDown ()
 {        
             StartCoroutine (TestDownload (imageURL[currentPage]));
 }
 
     private IEnumerator TestDownload (string uRL)
     {
         #if UNITY_ANDROID
 
         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);
         Application.OpenURL (savePath);
 
         #endif
     }
 }

BTW this isn`t optimized (user downloads the image every time hitting the button instead of first, checking if the image exists, if yes- open it. if not-download it.)

thanks!