Android mutable bitmap

It's about the same difference as with String vs StringBuilder - String is immutable so you can't change its content (well at least not without any hacks), while for StringBuilder you can change its content.

In order to convert an immutable bitmap to a mutable one, check out this post: https://stackoverflow.com/a/16314940/878126.

If your bitmap include mutable flag, its pixels can be change, if doesn't, pixel changings throw an error. It's the difference between them.

And here is Android: convert Immutable Bitmap into Mutable

Not sure if there is any performance gain for using immutable bitmaps. Often immutable is just for being thread safe (or if you are going to share the image with another process, process safe)