private static Bitmap createWaterMaskBitmap(Bitmap src, Bitmap watermark,
                        int paddingLeft, int paddingTop) {
    if (src == null) {
      return null;
    }
    int width = src.getWidth();
    int height = src.getHeight();
    //创建一个bitmap
    Bitmap newBitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);// 创建一个新的和SRC长度宽度一样的位图
    //将该图片作为画布
    Canvas canvas = new Canvas(newBitmap);
    //在画布 0，0坐标上开始绘制原始图片
    canvas.drawBitmap(src, 0, 0, null);
    //在画布上绘制水印图片
    canvas.drawBitmap(watermark, paddingLeft, paddingTop, null);
    // 保存
    canvas.save(Canvas.ALL_SAVE_FLAG);
    // 存储
    canvas.restore();
    return newBitmap;
  }

/**
   * 绘制文字到中间
   *
   * @param context
   * @param bitmap
   * @param text
   * @param size
   * @param color
   * @return
   */
  public static Bitmap drawTextToCenter(Context context, Bitmap bitmap, String text,
                     int size, int color) {
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(color);
    paint.setTextSize(dp2px(context, size));
    Rect bounds = new Rect();
    paint.getTextBounds(text, 0, text.length(), bounds);
    return drawTextToBitmap(context, bitmap, text, paint, bounds,
        (bitmap.getWidth() - bounds.width()) / 2,
        (bitmap.getHeight() + bounds.height()) / 2);
  }

  /**
   *  图片上绘制文字
   */
  private static Bitmap drawTextToBitmap(Context context, Bitmap bitmap, String text,
                      Paint paint, Rect bounds, int paddingLeft, int paddingTop) {
    Config bitmapConfig = bitmap.getConfig();

    paint.setDither(true); // 获取跟清晰的图像采样
    paint.setFilterBitmap(true);// 过滤一些
    if (bitmapConfig == null) {
      bitmapConfig = Config.ARGB_8888;
    }
    bitmap = bitmap.copy(bitmapConfig, true);
    Canvas canvas = new Canvas(bitmap);

    canvas.drawText(text, paddingLeft, paddingTop, paint);
    return bitmap;
  }