How Sobel Operator works in edge function?

Illustration
c_j - 2023-02-06T13:19:42+00:00
Question: How Sobel Operator works in edge function?

What does the edge function do when using the Sobel operator? How to automatically choosing a threshold? The edge is different from my own Sobel function.  

Related Questions

  • Imshow and Imshowpair differences?
  • Canny Edge Detection Threshold Values Meaning
  • How Sobel Operator works in edge function?
  • edge detection filters are not detecting my edges for the matrix

    • Expert Answer

    Profile picture of Prashant Kumar Prashant Kumar answered . 2025-11-20

    The sobel operator is used in Image processing edge detection, it works in the following manner
    1.) Compute gradient in X direction
    This can be done by multiple methods, simplest is to use conv2 function, call the resultant image Gx
    2.) Compute gradient in Y direction
    This can be done by multiple methods, simplest is to use conv2 function, call the resultant image Gy
    3.) Obtain magnitude of the resultant image
    I = sqrt(Gx*Gx + Gy*Gy)
    4.) Choose threshold based on application
     
    the following lines of code does all the above steps
     
    G  = imread('cameraman.tif')
Gx = conv2(G , [1 0 -1;...
                2 0 -2;...
                1 0 -1]); 
Gy = conv2(G , [1  2  1;...
                0  0  0;...
               -1 -2 -1]);
I = sqrt(Gx.*Gx + Gy.*Gy);
I_final = I > 150  % choose the thresold on your application need, experiment with different value to pick the best 
imshow(255*I_final)
    OR
    you can use the inbuilt function in MATLAB that does the same functionality
     
    I = imread('cameraman.tif');
I = edge(I, 'sobel') % there are also other operators like canny
imshow(I)

     


    Not satisfied with the answer ?? ASK NOW

    Get a Free Consultation or a Sample Assignment Review!

    Upload Assignment Talk to Expert