索贝尔边缘检测，图像卷积

Question

我正在处理一项使用图像上的索贝尔边缘检测的作业。我目前正在努力进行渐变操作。我在编译时收到 "bad operand types for binary operator '*'" 错误。我想这可能是因为我将所有像素都定义为字母，但我不确定下一步应该做什么。任何帮助将不胜感激！提前致谢！

public static BufferedImage sobelEdgeDetect(BufferedImage input) {
     int img_width = input.getWidth();
    int img_height = input.getHeight();

    BufferedImage output_img = new BufferedImage(
        img_width, img_height, BufferedImage.TYPE_INT_RGB);

    for (int x = 0; x < img_width; x++) {
      for (int y = 0; y < img_height; y++) {

    Color color_at_pos = new Color(input.getRGB(x, y));

    int red = color_at_pos.getRed();
    int green = color_at_pos.getGreen();
    int blue = color_at_pos.getBlue();

    int average = (red + green + blue) / 3;

    Color A,B,C,D,F,G,H,I;

    if(x-1 > 0 && y+1 < img_height){
          A = new Color (input.getRGB(x-1,y+1));
        } else {
          A = Color.BLACK;
        }

        if(y+1 < img_height){
          B = new Color (input.getRGB(x,y+1));
        } else {
          B = Color.BLACK;
        }

        if(x+1 < img_width && y+1 < img_height){
          C = new Color (input.getRGB(x+1,y+1));
        } else {
          C = Color.BLACK;
        }

        if(x-1 > 0){
          D = new Color (input.getRGB(x-1,y));
        } else {
          D = Color.BLACK;
        }

        if(x+1 < img_width){
          F = new Color (input.getRGB(x+1,y));
        } else {
          F = Color.BLACK;
        }

        if(x-1 > 0 && y-1 > 0){
          G = new Color (input.getRGB(x-1,y-1));
        } else {
          G = Color.BLACK;
        }

        if(y-1 > 0){
          H = new Color (input.getRGB(x,y-1));
        } else {
          H = Color.BLACK;
        }

        if(x+1 > img_width && y-1 > 0){
          I = new Color (input.getRGB(x+1,y-1));
        } else {
          I = Color.BLACK;
        }

       int gx = (-A + (-2*D) + -G + C + (2*F)+ I);
       int gy = (A + (2*B) + C + (-G) + (-2*H) + (-I));

      int result = (int)math.sqrt((gx*gx) + (gy*gy));

        if (average < 0) {
          average = 0;
        } else if (average > 255) {
          average = 255;
        }

        Color average_color = new Color(average, average, average);

        output_img.setRGB(x, y, average_color.getRGB());
      }
    } 
     return output_img;
  }

Answer 1

问题出在颜色的处理上，这里：

int gx = (-A + (-2*D) + -G + C + (2*F)+ I);
int gy = (A + (2*B) + C + (-G) + (-2*H) + (-I));

这行不通。

要获得渐变，您必须

分别处理每种颜色
处理灰度图像

我不能告诉你哪一个适合你。

分别处理每种颜色：

使用这种方法，您可以单独处理每种颜色以检测该颜色的边缘

//red:
int redGx = (-A.getRed() + (-2*D.getRed()) + -G.getRed() + C.getRed() + (2*F.getRed())+ I.getRed());
int redGy = ...

//green:
int greenGx = (-A.getGreen()...

处理为灰色

int redGx = (toGray(A) + (-2*toGray(D)) + -toGray(G) + toGray(C) + (2*toGray(F))+ toGray(I));
int redGy = ...

你必须提供方法toGray/平均颜色

static int toGray(Color col){
    return (color.getGreen()+color.getRed()+col.getBlue()) / 3;
}

索贝尔边缘检测，图像卷积

Sobel Edge Detection, image convolution

java

convolution

edge-detection

sobel

分别处理每种颜色：

处理为灰色