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matlabedge-detectionsobel

How to colour the edges after using sobel filter?

I am using sobel filter for edge detection. How to illustrate the gradient direction with color coding. For example, horizontal edges with blue and vertical edges with yellow?

Thank you.

Solution

  • Since you can specify whether you want horizontal or vertical edge detected (check here), you could perform 2 filtering operations (one horizontal and the other vertical) and save each resulting image, then concatenating them to form a final, 3-channels RGB image.

    The RGB color code for yellow is [1 1 0] and that of blue is [0 0 1], so in your case the vertical edge image will occupy the first 2 channels whereas the horizontal edge image will occupy the last channel.

    Example:

    clear
clc
close all

A = imread('circuit.tif');

[r,c,~] = size(A);

EdgeH = edge(A,'Sobel','Horizontal');
EdgeV = edge(A,'Sobel','Vertical');

%// Arrange the binary images to form a RGB color image.
FinalIm = zeros(r,c,3,'uint8');

FinalIm(:,:,1) = 255*EdgeV;
FinalIm(:,:,2) = 255*EdgeV;
FinalIm(:,:,3) = 255*EdgeH;

figure;

subplot(1,2,1)
imshow(A)

subplot(1,2,2)
imshow(FinalIm)

    Output:

    enter image description here