Рисование

canvas.drawBitmap (background, matrix, paint);
canvas.drawBitmap (foreground, matrix, paint);

Paint p = new Paint();
p.setAlpha(127);

package com.example.touchdrawv2;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.PorterDuff.Mode;
import android.util.Log;
import android.view.Menu;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
 
public class TouchDrawv2 extends Activity implements SurfaceHolder.Callback {
 
    private static final String TAG = "Svetlin SurfaceView";
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        SurfaceView view = new SurfaceView(this);
        setContentView(view);
        view.getHolder().addCallback(this);
    }
 
    public void surfaceCreated(SurfaceHolder holder) {
        tryDrawing(holder);
    }
 
    public void surfaceChanged(SurfaceHolder holder, int frmt, int w, int h) { 
        tryDrawing(holder);
    }
 
    public void surfaceDestroyed(SurfaceHolder holder) {}
 
    private void tryDrawing(SurfaceHolder holder) {
      
 
        Canvas canvas = holder.lockCanvas();
        if (canvas == null) {
            Log.e(TAG, "Cannot draw onto the canvas as it's null");
        } else {
            drawMyStuff(canvas);
            holder.unlockCanvasAndPost(canvas);
        }
    }
 
    private void drawMyStuff(final Canvas canvas) {
 
       // canvas.drawRGB(255, 0, 0);
        canvas.drawColor(Color.TRANSPARENT, Mode.CLEAR);
    }
}

SurfaceView.setZOrderOnTop(true);
SurfaceView.getHolder().setFormat(PixelFormat.TRANSPARENT);