添加水印的方法挺简单的

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ImageView iv = (ImageView) findViewById(R.id.imageView);
        Drawable drawable = ContextCompat.getDrawable(this, R.drawable.image);
        BitmapDrawable bd = (BitmapDrawable) drawable;
        Bitmap bmp = bd.getBitmap();
        Bitmap bitmap = createWatermark(bmp, "叶应是叶" + "http://blog.csdn.net/new_one_object");
        iv.setImageBitmap(bitmap);
    }

    private Bitmap createWatermark(Bitmap bitmap, String mark) {
        int w = bitmap.getWidth();
        int h = bitmap.getHeight();
        Bitmap bmp = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bmp);
        Paint p = new Paint();
        // 水印颜色
        p.setColor(Color.parseColor("#c5576370"));
        // 水印字体大小
        p.setTextSize(150);
        //抗锯齿
        p.setAntiAlias(true);
        //绘制图像
        canvas.drawBitmap(bitmap, 0, 0, p);
        //绘制文字
        canvas.drawText(mark, 0, h / 2, p);
        canvas.save(Canvas.ALL_SAVE_FLAG);
        canvas.restore();
        return bmp;
    }

}

效果图

这里写图片描述