code: @Nullable
      public static Bitmap mutable(Bitmap source) {
          if (source.isMutable()) {
              return source;
          }
          Config config = source.getConfig();
          Bitmap bm = source.copy(config != null ? config : ARGB_8888, true);
          if (bm != null) {
              source.recycle();
          }
          return bm;
      }
docs: If the bitmap is immutable, get a mutable copy of it. After a copy is created, the source
  bitmap will be recycled. If the bitmap is already mutable, it will be returned.
  
  @return null if a copy could not be made