Reference to http://developer.android.com/guide/topics/data/data-storage.html#filesInternal

Saving of images into internal storage

FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
fos.write(string.getBytes());
fos.close();

Displaying of images from internal storage

FileInputStream in = openFileInput(FILENAME);
Bitmap image = BitmapFactory.decodeStream(in);
imageView.setImageBitmap(image);