title: React Native save a http Image to Android camera roll
body: <p>Here are some images from websites and I want to save them to Android camera roll.</p>
  
  <p>I found out that React Native has an function <code>CameraRoll.saveImageWithTag</code> which could save certain image into the camera roll, but the param <code>tag</code> should be a local URI, such as <code>"file:///sdcard/img.png"</code>. So how to save the image in Android React Native if the image source was not local?</p>