Simple Green Screen images for Android

gistfile1.java

//This demo app Assumes there are 2 jpg files on the sdcard in the root directory

public class MainActivity extends ActionBarActivity {

	ImageView img;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		img = (ImageView) findViewById(R.id.img);

		String path = Environment.getExternalStorageDirectory()
				.getAbsolutePath();

		BitmapFactory.Options options = new BitmapFactory.Options();
		options.inPreferredConfig = Bitmap.Config.ARGB_8888;
		Bitmap greenBitmap = BitmapFactory.decodeFile(path + "/green.jpg",
				options);
		Bitmap bkgBitmap = BitmapFactory.decodeFile(path + "/bkg.jpg", options);

		Bitmap[] arr = new Bitmap[] { greenBitmap, bkgBitmap };

		new Async().execute(arr);

	}

	private class Async extends AsyncTask<Bitmap[], Void, Bitmap> {

		@Override
		protected Bitmap doInBackground(Bitmap[]... params) {

			Bitmap newBitmap = null;
			try {
				newBitmap = getCompositedImage(params[0]);
			} catch (Exception e) {
				e.printStackTrace();
			}
			return newBitmap;
		}

		@Override
		protected void onPostExecute(Bitmap newBitmap) {
			super.onPostExecute(newBitmap);

			img.setImageBitmap(newBitmap);
		}
	}

	private static Bitmap getCompositedImage(Bitmap[] images) throws Exception {
		if (images[0].getWidth() != images[1].getWidth()
				&& images[0].getHeight() != images[1].getHeight())
			throw new Exception("The images are different sized...");

		Bitmap compositeBitmap = Bitmap.createBitmap(images[0].getWidth(),
				images[0].getHeight(), Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas(compositeBitmap);

		Paint paint = new Paint();
		paint.setStyle(Paint.Style.FILL);

		for (int x = 0; x < canvas.getWidth(); x++) {
			for (int y = 0; y < canvas.getHeight(); y++) {
				int greenScreenPixel = images[0].getPixel(x, y);
				int bgPixel = images[1].getPixel(x, y);

				int pixelGreenVal = Color.green(greenScreenPixel);
				int pixelRedVal = Color.red(greenScreenPixel);
				int pixelBlueVal = Color.blue(greenScreenPixel);

				if (pixelGreenVal > pixelRedVal + pixelBlueVal) {
					paint.setColor(bgPixel);
					canvas.drawPoint(x, y, paint);
				} else {
					paint.setColor(greenScreenPixel);
					canvas.drawPoint(x, y, paint);
				}
			}
		}
		return compositeBitmap;
	}
}