Android在ImageView上做一些涂鸦

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.nanana).copy(Bitmap.Config.ARGB_8888, true);
Canvas canvas = new Canvas(bitmap);
String text = "666";
Rect rect = new Rect();
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setTextSize(30);
paint.getTextBounds(text, 0, text.length(), rect);
canvas.drawText(text, (bitmap.getWidth() - rect.width())>>1, (bitmap.getHeight() + rect.height())>>1, paint);
canvas.save();
ImageView iv = (ImageView) findViewById(R.id.iv);
iv.setImageBitmap(bitmap);