Can't import javax.imageio.ImageIO in Android application
You have tagged your question with Android. javax.imageio.ImageIO is not part of the Android platform, so unfortunately you can't use it. Instead you need to use what's available in the Android SDK for reading and storing images.
Have a look at the Bitmap and BitmapFactory classes for a starting point.
These classes contains the necessary methods to read (BitmapFactory.decode*(...) methods) and write (Bitmap.compress(...) method).