图片的合成

public class MainActivity extends Activity {

private ImageView iv;

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

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

//图片合成，画布一张，先画图片A， 再画图片B
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.aa);

Bitmap alterBitmap = Bitmap.createBitmap(bitmap.getWidth()
, bitmap.getHeight()
, bitmap.getConfig());

Canvas canvas = new Canvas(alterBitmap);
Paint paint = new Paint();
paint.setColor(Color.BLACK);

paint.setXfermode(new PorterDuffXfermode(Mode.LIGHTEN));

canvas.drawBitmap(bitmap, new Matrix(), paint);
Bitmap ic_launcher = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
canvas.drawBitmap(ic_launcher, new Matrix(), paint);

iv.setImageBitmap(alterBitmap);

}

}