i am unable to zigzag scan image

i am using this code kindly help me to solve

https://in.mathworks.com/matlabcentral/fileexchange/56332-zigzag-scan-any-n-n-matrix--bloc-of-image-

[Walter Roberson]

Are you getting an error message? If so then please post the complete message.

What is size() of the image you are passing to the routine?

[juveria fatima]

am using lena image

X=imread('lena1.jpg');
  imshow(X);
  function Vect=ZigZagscan(X)
  % ZigZagscan Transform an matrix to a vector using Zig Zag Scan.
  %    
  % VECT = ZIGZAGSCAN(MATRIX) reorganize the input Matrix and output it as a vector.
  %    
  %    Example:
  %          X=[1 2 3
  %             4 5 6
  %             7 8 9]

    %     X =
    %        1  2  3
    %        4  5  6
    %        7  8  9
    %
    %     ZigZagscan(X)=
    %                   1  2  4  7  5  3  6  8  9
    %
    %**************************************************************************
    % Autors : Said BOUREZG   
    % Engineer on Electronics  option: Communication .
    % Date : 08.03.2016
    % Filename ZigZagscan.m  
    % Please contribute if you find this software useful.
    % Report bugs to: [e-mail]
    % Adress:                         Said BOUREZG
    %                                El Hodhna Street
    %                                 28038 Tarmount
    %                                M'sila - Algeria 
    % Email: [e-mail]
    % Mobile: [phone] 
    % http://
    % If you can improve this code furtherly or add ...,
    % please let me know. Thanks
    %**************************************************************************
    % X=imread('pingu.jpg');
    % imshow(X);

    [~, N]=size(X);
    Vect=zeros(1,N*N);
    Vect(1)=X(1,1);
    v=1;
    for k=1:2*N-1
        if k<=N
              if mod(k,2)==0
               j=k;
                  for i=1:k
                  Vect(v)=X(i,j);
                  v=v+1;j=j-1;    
                  end
              else
                  i=k;
                  for j=1:k   
                  Vect(v)=X(i,j);
                  v=v+1;i=i-1; 
                  end
               end
        else
               if mod(k,2)==0
                p=mod(k,N); j=N;
                    for i=p+1:N
                    Vect(v)=X(i,j);   
                    end
                    v=v+1;j=j-1; 
               else
                p=mod(k,N);i=N;
                     for j=p+1:N   
                     Vect(v)=X(i,j);
                     v=v+1;i=i-1; 
                     end
                end
        end
    end
    end

[Walter Roberson]

What error message are you seeing?

[juveria fatima]

as u said to apply on one channel i tried

am getting this error

Error in ZigZagscan (line 41)
Vect=zeros(1,N*N);
Error in zz (line 7)
 Vect= ZigZagscan(X);

this way am applying one channel to zigzag scan

A= imread('lena1.jpg');
Red = A(:,:,1);
X = reshape(uint8(Red), [1 size(Red)]);
   Vect= ZigZagscan(X);

i am unable to find the error please help me out

this is working very fine if i input this

X=[1 2 3
            4 5 6
            7 8 9]

[Walter Roberson]

Why are you reshaping Red into a 3D array? Why are you reshaping it at all? Why not just ZigZagscan(red) ?

[juveria fatima]

thank you very much, it worked.

Answer 1

[Guillaume]

You cannot copy the body of a function into your code and expect it to work like a script. The function needs to be in its own m-file which you call from your script. Hence your script should only be:

X=imread('lena1.jpg');
imshow(X);
v = ZigZagScan(X);

Saying that, this ZigZagScan function is not particularly well written and assumes the input is a square matrix.

Below, a simpler code. Note this is also a function, so you'll have to put it into its own m-file named antizigzag.m

function v = antizigzag(X)
   %author: G. de Sercey, University of Brighton
   %BSD license
   %input: X a 2D matrix, not necessarily square
   %output: v a row vector of the anti-diagonals of the matrix scanned in a zigzag fashion

     validateattributes(X, {'numeric'}, {'2d'});
     X = fliplr(X);  %flip X so the anti-diagonals become diagonals
     v = arrayfun(@(d) diag(X, d), size(X, 2)-1:-1:1-size(X, 1), 'UniformOutput', false);  %get the diagonals
     v(1:2:end) = cellfun(@flip, v(1:2:end), 'UniformOutput', false);  %flip odd diagonals
     v = vertcat(v{:}).';  %concatenate the whole lot in a row vector
  end

[juveria fatima]

still am getting dimension error as

Index exceeds matrix dimensions. Error in ZigZagscan (line 55) Vect(v)=X(i,j);

[Guillaume]

As I said, I don't think that the code you found is of particularly good quality and I'm certainly not going to debug the mistakes that the author has made. In particular, the code assume that the input is a square matrix so if your input is not square, it will error.

Why don't you use the code I've provided which is much simpler and produces the same result (and works even if the input matrix is not square)?

[juveria fatima]

can you please share your code link

[Guillaume]

It's right up there ^ in my answer!

Copy/paste the code starting at

function v = antizigzag(X)
   %...

into a new file, that you'll name antizigzag.m. You can then call it from your own code

X=imread('lena1.jpg');
imshow(X);
v = antizigzag(X);

[juveria fatima]

am getting error

Error using antizigzag (line 6)
Expected input to be two-dimensional.

[Walter Roberson]

jpeg images are 3 dimensional more than 99.9% of the time. You cannot apply zigzag or anti-zigzag routines to them as a whole: you can only apply it to one channel at a time, or else reshape the whole thing as if it were 2D and process the reshaped version. Or convert to grayscale and work with that.

[juveria fatima]

as u said to apply on one channel i tried

am getting this error

Error in ZigZagscan (line 41)
Vect=zeros(1,N*N);

Error in zz (line 7)
 Vect= ZigZagscan(X);

this way am applying one channel to zigzag scan

A= imread('lena1.jpg');
Red = A(:,:,1);
X = reshape(uint8(Red), [1 size(Red)]);

   Vect= ZigZagscan(X);

i am unable to find the error please help me out

this is working very fine if i input this

X=[1 2 3
            4 5 6
            7 8 9]