Ionic v3 - Convert local image to base64

I need to use an image taken with Camera and/or Library and send it to Firebase, I made use of the following native plugins in order:

After that I use the “putString” function of angularfire2 and works perfectly on Android, but in IOS the execution for the Base64 plugin, either with camera image or Bibioteca does not return any error.

I tried the common conversion by JS but it is not allowed by CORS, is there any alternative to base64 plugin?