Например:
InputStream is = new FileInputStream(new File(Environment.getExternalStorageDirectory(), "image.tmp"););
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 4; //subsampling
int compress = 75;
BitmapFactory.decodeStream(is, null, options).compress(CompressFormat.JPEG, compress, new FileOutputStream(file));
Это грязный пример. Используйте try catch, null check и т. Д.