Thursday, January 19, 2012

Android Bitmap Idiosyncrasies

Whilst improving my Android app Chromakey Photo Edit, I've come across a few idiosyncrasies with Android Bitmaps which I thought I'd share for reference:-

  • Bitmap.createScaledBitmap() always returns a bitmap of type RGB_565, regardless of the source bitmap.  See
  • ARGB_4444 is now depreciated, so you'll always need to use ARGB_8888 if you want to store transparency information.
  • When using BitmapFactory.decodeFile(), always try to pass a BitmapFactory.Options().inPreferredConfig to ensure you get a bitmap in the format you need.  By default, bitmaps loaded this way are always immutable (uneditable), so you'll need to do a Bitmap.copy() if you need to make it mutable.
  • Bitmap.recycle() is ALWAYS required; if you create a bitmap but don't recycle when you're finished with it, expect to run out of memory eventually.  Setting bitmaps to null isn't necessary.