Opencv C++ 用卷积核给图片加白边

如果一张图片的背景是黑色，上面的内容是蓝色，那么怎么给蓝色的内容加上白边呢？

方法是用卷积核遍历每个像素点，如果同一个核内既有蓝点也有黑点，那么将卷积核内的黑点变成白点，这样就形成了白边。代码如下：

  void add_shader(cv::Mat& img, int core = 2)
  {
    int w = img.cols, h = img.rows; int row_size = (int)img.step, p_size =(int)img.elemSize();
    uchar* d, * row;

    d = img.data; row = d; row += row_size * core; d = row + p_size * core;
    for (int i = core; i < h - core; i++)
    {
      for (int j = core; j < w - core; j++)
      {
        if (d[0] == 255 && d[1] == 0 && d[2] == 0) // blue pixel
        {

          bool hasBlack = false;
          for (int pi = -core; pi <= core; pi++)
          {
            for (int pj = -core; pj <= core; pj++)
            {
              auto pd = d + pi * row_size + pj * p_size;              
              if (pd[0] == 0 && pd[1] == 0 && pd[2] == 0) { hasBlack = true; goto end; }
            }
          }
          end:
          if (hasBlack)
          {
            for (int pi = -core; pi <= core; pi++)
            {
              for (int pj = -core; pj <= core; pj++)
              {
                auto pd = d + pi * row_size + pj * p_size;
                if (pd[0] == 0 && pd[1] == 0 && pd[2] == 0) { pd[0] = pd[1] = pd[2] = pd[3] = 255; }
              }
            }
          }
        }

        d += p_size;
      }
      row += row_size; d = row + p_size * core;
    }
  }