Code for png image using sobel operator

cc = imread('CocaCola.png');

cc = imread('CocaCola.png');
cc = uint8(cc); 
figure, imshow(cc); title('cc'); 

cc = rgb2gray(cc); 
 
cc = double(cc); 

edg = edgy(cc);

% Pre-allocate the filtered_image matrix with zeros 
edg = zeros(size(cc)); 

Mx = [-1 0 1; -2 0 2; -1 0 1]; 
My = [-1 -2 -1; 0 0 0; 1 2 1]; 


for i = 1:size(cc, 1) - 2 
	for j = 1:size(cc, 2) - 2 

		% Gradient approximations 
		Gx = sum(sum(Mx.*cc(i:i+2, j:j+2))); 
		Gy = sum(sum(My.*cc(i:i+2, j:j+2))); 
				
		% Calculate magnitude of vector 
		edg(i+1, j+1) = sqrt(Gx.^2 + Gy.^2); 
		
	end
end


edg = uint8(edg); 
figure, imshow(edg); title('edg'); 


thresholdValue = 100; % varies between [0 255] 
output_image = max(edg, thresholdValue); 
output_image(output_image == round(thresholdValue)) = 0; 


output_image = im2bw(output_image); 
figure, imshow(output_image); title('Edge Detected Image'); 

I wrote this code but did't work .please help

Answer 1

[Fatih Yurekli]

function [c3] = edgy(c)
s1 = [-1 0 1;-2 0 2;-1 0 1];
s1 = double(s1);

s2 = [1 2 1; 0 0 0;-1 -2 -1];
s2 = double(s2);

c = double(c);
[M N] = size(c);
for i = 1:M-2
    for j = 1:N-2
        a = c(i:i+2, j:j+2);
        a1 = a.*s1;
        a2 = a.*s2;
        b1= 0;
        b2= 0;
        for  k = 1:3
         for  l = 1:3
            b1 = b1+a1(k,l);
            b2 = b2+a2(k,l);
        end
        end
    c1(i,j) =b1;
    c2(i,j) = b2;
    end
end
c3 = sqrt(c1.^2+c2.^2);
c3 = uint8(c3);
end

[ABHIJIT BISWAS]

works fine for me. Thank you.

[PRASANTH R]

c3 is not working bro in 28th line

[Walter Roberson]

Do you mean the uint8() line? What error message are you encountering?

[PRASANTH R]

Undefined function 'unit8' for input arguments of type 'double'.

Error in edgy (line 28)

c3= unit8(c3)

[PRASANTH R]

i used the same program given above but it showing error in line 28 please help me

[Walter Roberson]

you mistyped as unit8 instead of uint8

[PRASANTH R]

[PRASANTH R]

after all the program it says like this as incorrect value help me

[Walter Roberson]

you are required to assign to a variable named output . Not output_image

[PRASANTH R]

can you please give me a code im confused at all please help me brother

[PRASANTH R]

mr.walter please answer my question

[Walter Roberson]

wrong:

output_image = im2bw(output_image);

Better:

   output = im2bw(output_image);

[Walter Roberson]

Note: it is 7am my time and I have been up all night doing research and answering questions. I am in bed, assisting multiple people at the same time, and hoping to fall asleep.

[Image Analyst]

Prashanth, you know you can click the "Copy code" icon in the upper right of the code blocks here in answers. You don't have to re-type all this in to your MATLAB, which could introduce typos.

Answer 2

[Sulaymon Eshkabilov]

Hi,

Here is the simple solution with MATLAB's builtin function of Image Processing Toolbox that works quite well:

COCA = imread('CC.png');
BW1 = edge(COCA,'sobel');
figure;
imshow(BW1)
title('Sobel Filter');

[Mohaiminul Islam]

didn,t work . could you please write code according to the question given above.

[Mohaiminul Islam]

Answer 3

[Génesis Vivas]

Hi friend, I think that your problem is that you started in for i = 1:size(cc, 1) - 2, you shouldnt take the border, i=1, what you should do is start from the second position both in the rows and in the columns, and stake out the sums Mx and My, and done!

for i = 2:rows-1
	for j = 2:columns-1

[Image Analyst]

His original indexing code would have had no problem - it never went outside the image. Though most people would have done it like you did. The real problem (and what threw the error) was that he did this:

edg = edgy(cc);

without ever having written edgy function and either saving that in a file on the path (like the current folder), or having it defined down below in his script. You can't call a function if it's not defined and it has to be defined either

1. in the same script, with the "function" keyword down below the script part of the file, OR
2. in a separate m-file.