EDGE function ERROR
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I'm trying to perform the following operation
%Load the image into matlab
A = imread('before3.jpg');
%Show the image
figure(1)
imshow(A)
I = edge(A, 'sobel');
Using this high pass filter I expect to find the edges of my image but I get the following error while using the edge function.
??? Function EDGE expected its first input, I, to be two-dimensional.
Error in ==> edge>parse_inputs at 564
iptcheckinput(I,{'numeric'},{'nonsparse','2d'},mfilename,'I',1);
Error in ==> edge at 197
[a,method,thresh,sigma,thinning,H,kx,ky] = parse_inputs(varargin{:});
Error in ==> image1 at 21
I = edge(A,'sobel');
The image 'before3.jpg' has value
<1728x2304x3 uint8>
The error says to use a 2 dimensional input but I have not been able to find a way to change my image to a 2 dimensional matrix and keep at the same time the original edges.
I tried
[X, map] = rgb2ind(A,256);
I used as the map a 'gray' scale but it did not work.
Please if you have a different approach that you can recommend me I will be very grateful.
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Answers (7)
JOEL
on 1 Oct 2014
Edited: DGM
on 11 Feb 2023
EFECTIVAMENTE AMIGO, LA FUNCION edge SOLO ADMITE IMAGEN ES ESCALAS GRISES, REALIZA LO SIGUIENTE:
%para leer una imagen
I = imread('casa.jpg');
%% convertir a escalas grises
I=rgb2gray(I);
%hallando contorno
BW = edge(I);
%mostrando contorno
imshow(BW)
slds,
Joel Villavicencio
3 Comments
Muddasar Khan
on 19 Feb 2018
Yes, You are right. We should convert colored image to gray image then edges should be detected
Jan
on 17 Nov 2011
In the help text of edge I find:
W = edge(I) takes a grayscale or a binary image I as its input...
Alex
on 17 Nov 2011
according to the documentation, using imread with a jpeg object results in RGB scale. As in, each pixel is represented by a 3 element vector ['red value' 'green value' 'blue value'];
1 Comment
Walter Roberson
on 19 Feb 2018
Not universally true. There are true grayscale jpeg images. But I have only ever encountered one, apart from test images to prove that they exist. Jpeg is nearly always rgb. Never pseudocolor though.
Eulises Ulloa
on 17 Nov 2011
3 Comments
Jan
on 17 Nov 2011
If you want to use the edge-detection on an RGB image, you cannot use the EDGE function. There are a lot of edge-detection methods in the FEX: http://www.mathworks.com/matlabcentral/fileexchange/?term=edge
There are other methods to convert the image to gray-scale also. Consider to sharpen the edges in the HSV color-space at first.
Priscil23
on 15 Feb 2018
Just as everyone said, first convert your rgb2gray then to view the output after your desired edge functions use imshow to view the image. I faced the same problem.
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priyanka nale
on 30 Dec 2019
close all;
clear ;
I=imread('4.jpg');
figure,imshow(I)
I=rgb2gray(I);
c= edge(I,'sobel');
figure,imshow(c);
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