java - 在 Java 中实现 Sobel 过滤器 - 标准化值

Question

我想自己实现Sobel Filter(实际上没有漂亮的实现)。但是在进行卷积之后我不知道如何计算 rgb 值。

• 假设:灰度图像

  double [][] sobel_x = 
  {
      { -1, 0, 1},
      { -2, 0, 2},
      { -1, 0, 1}
  };
  
  double [][]    sobel_y = 
  {
      { 1, 2, 1},
      { 0, 0, 0},
      {-1, -2, 1}
  };
  
  for(int y=1; y<image.getHeight()-1; y++)
  {
      for(int x=1; x<image.getWidth()-1; x++)
      {
         Color a = new Color(image.getRGB(x-1, y-1));
         Color b = new Color(image.getRGB(x, y-1));
         Color c = new Color(image.getRGB(x+1, y-1));
         Color d = new Color(image.getRGB(x-1, y));
         Color e = new Color(image.getRGB(x, y));
         Color f = new Color(image.getRGB(x+1, y));
         Color g = new Color(image.getRGB(x-1, y+1));
         Color h = new Color(image.getRGB(x, y+1));
         Color i = new Color(image.getRGB(x+1, y+1));
  
          double pixel_x =    (sobel_x[0][0] * a.getRed()) + (sobel_x[0][1] * b.getRed()) + (sobel_x[0][2] * c.getRed()) +
                              (sobel_x[1][0] * d.getRed())   + (sobel_x[1][1] * e.getRed())   + (sobel_x[1][2] * f.getRed()) +
                              (sobel_x[2][0] * g.getRed()) + (sobel_x[2][1] * h.getRed()) + (sobel_x[2][2] * i.getRed());
          double pixel_y = 
                              (sobel_y[0][0] * a.getRed()) + (sobel_x[0][1] * b.getRed()) + (sobel_x[0][2] * c.getRed()) +
                              (sobel_y[1][0] * d.getRed())   + (sobel_x[1][1] * e.getRed())   + (sobel_x[1][2] * f.getRed()) +
                              (sobel_y[2][0] * g.getRed()) + (sobel_x[2][1] * h.getRed()) + (sobel_x[2][2] * i.getRed());  
  
          //Here it is possible to get values between [-1020, 1020]       
  
          //How to going on
  
          //int rgb = (int) Math.sqrt(pixel_x*pixel_x+pixel_y*pixel_y);
  
          //int rgbAsInt = (int)(65536 * rgb + 256 * rgb + rgb);      
      }
  }   
  

Answer 1

我的想法之一是进行线性变换。例如，您得到的图像中的最小像素值为-998，最大像素值为1000。因此您可以将-998对应于0，将1000对应于255，然后得到(-998,1000)的比例尺与刻度为 (0,255)，并将 [-998,1000] 到 [0,255] 之间的所有值标准化。