Code for png image using sobel operator
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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
回答（3 个）
Fatih Yurekli
2020-10-16
编辑：Walter Roberson
2020-12-27
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
14 个评论
ABHIJIT BISWAS
2020-12-23
works fine for me. Thank you.
PRASANTH R
2020-12-27
c3 is not working bro in 28th line
Walter Roberson
2020-12-27
Do you mean the uint8() line? What error message are you encountering?
PRASANTH R
2020-12-27
Undefined function 'unit8' for input arguments of type 'double'.
Error in edgy (line 28)
c3= unit8(c3)
PRASANTH R
2020-12-27
i used the same program given above but it showing error in line 28 please help me
Walter Roberson
2020-12-27
you mistyped as unit8 instead of uint8
PRASANTH R
2020-12-27
PRASANTH R
2020-12-27
after all the program it says like this as incorrect value help me
Walter Roberson
2020-12-27
you are required to assign to a variable named output . Not output_image
PRASANTH R
2020-12-27
can you please give me a code im confused at all please help me brother
PRASANTH R
2020-12-27
mr.walter please answer my question
Walter Roberson
2020-12-27
wrong:
output_image = im2bw(output_image);
Better:
output = im2bw(output_image);
Walter Roberson
2020-12-27
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
2020-12-27
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.
Sulaymon Eshkabilov
2020-9-7
编辑：Sulaymon Eshkabilov
2020-9-7
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');
Génesis Vivas
2020-9-24
编辑：Génesis Vivas
2020-9-24
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
1 个评论
Image Analyst
2020-12-27
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
- in the same script, with the "function" keyword down below the script part of the file, OR
- in a separate m-file.
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