Code for png image using sobel operator

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Mohaiminul Islam
Mohaiminul Islam 2020-9-7
评论： Image Analyst 2020-12-27
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

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回答（3 个）

Fatih Yurekli
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
显示 12更早的评论
Walter Roberson
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
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.

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

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