What is the comments given in this IWT code?

Hello,

I am not able to read and understand the comments given in the following code.I got this from net and also not able to understand steps followed in this code.Please help me in this regard.

   function y=IWT(x)  
   x=imread('lenna.gif'); 
   subplot(2,3,1);imshow(x);title('ԭͼÏñ'); 
   x=double(x); 
   y=x;  
   [hp,lp]=size(x); 
   hc=hp/2;  lc=lp/2;
   %----------------ÆæżÁÐÖØÅÅ 
   for n=1:lc          
      j=n*2-1;          
      y(:,n)=x(:,j);         
      y(:,lc+n)=x(:,j+1); 
  end 
   subplot(2,3,2);imshow(uint8(y)); title('ÆæżÁÐÖØÅÅ');
   %-----------------ÐÐÖØÅÅ  
   for n=1:lc         
      y(:,lc+n)=y(:,lc+n)-y(:,n); 
   end  
   for n=1:lc         
      k=y(:,lc+n)/2-mod(y(:,lc+n)/2,1);       
      y(:,n)=y(:,n)+k; 
   end 
   subplot(2,3,3);imshow(uint8(y));title('ÐÐÖØÅÅ');  
   %---------------ÆæżÐÐÖØÅÅ 
   x=y;
   for n=1:hc         
      j=n*2-1;          
      y(n,:)=x(j,:);          
      y(hc+n,:)=x(j+1,:);  
   end 
   subplot(2,3,4);imshow(uint8(y));title('ÆæżÐÐÖØÅÅ'); 
   %---------------ÁÐÖØÅÅ 
   for n=1:hc          
      y(hc+n,:)=y(hc+n,:)-y(n,:); 
  end  
  for n=1:hc          
      k=y(hc+n,:)/2-mod(y(hc+n,:)/2,1);          
      y(n,:)=y(n,:)+k; 
  end  
  subplot(2,3,5);imshow(uint8(y));title('ÁÐÖØÅÅ');
  %----------------Öظ´ÉÏÊö²½Ö裬½øÐжþ´ÎѹËõ  
  for n=1:lc          
      j=n*2-1;         
      y(:,n)=x(:,j);          
      y(:,lc+n)=x(:,j+1); 
  end   
  for n=1:lc           
      y(:,lc+n)=y(:,lc+n)-y(:,n); 
  end 
  for n=1:lc           
      k=y(:,lc+n)/2-mod(y(:,lc+n)/2,1);        
      y(:,n)=y(:,n)+k;
  end   
  x=y;  
  for n=1:hc      
      j=n*2-1;      
      y(n,:)=x(j,:);       
      y(hc+n,:)=x(j+1,:); 
  end  
  for n=1:hc    
      y(hc+n,:)=y(hc+n,:)-y(n,:); 
  end  
  for n=1:hc       
      k=y(hc+n,:)/2-mod(y(hc+n,:)/2,1);     
      y(n,:)=y(n,:)+k; 
  end
  %----------------ÔÙ½øÐÐÆæżÐÐÖØÅźÍÁÐÖØÅÅ  
  x=y;  
  for n=1:hc    
      j=n*2-1;     
      y(n,:)=x(j,:);   
      y(hc+n,:)=x(j+1,:); 
  end   
  for n=1:hc  
      y(hc+n,:)=y(hc+n,:)-y(n,:); 
  end 
  for n=1:hc     
      k=y(hc+n,:)/2-mod(y(hc+n,:)/2,1);     
      y(n,:)=y(n,:)+k; 
  end
  subplot(2,3,6);imshow(uint8(y));title('¶þ´ÎѹËõ ');

[Sara msr]

this code was very useful. Do you also have the inverse iwt code? i realy need it.

[Walter Roberson]

The comments that show up here are comments originally written in UTF-8 but the code has been saved as if it were ASCII and the extra bytes needed to decode it have been lost.

I do not happen to find a copy of the original code anywhere; if the original were available then the comments could be run through a translator.

[nur aqila]

hye sara, im having the same problem as you. I dont know how to do inverse iwt. have found the solution ?

[rizky alvarez]

hi sara and nur, so do i, i m still not understand waht the meaning on this code, have find the solution what is the meaning on this code ?

[Walter Roberson]

@rizky alvarez

Have you managed to find an original source for the code? (Something other than this post) ?

Answer 1

[Wayne King]

I think you have to inquire with the individuals that provided this code.

Do you have the MathWorks Wavelet Toolbox? If so you can implement both the 2-D DWT and the inverse DWT using that Toolbox.

[Pooja]

Hello,

There is no identity of the author.`when i gave code like this i got o/p in this form

x=imread('lena.bmp');
y=dwt2(x)

o/p -Error in ==> Untitled5 at 2
y=dwt2(x) 
??? Error using ==> dwt2 at 55
Not enough input arguments.

What is the problem?

Answer 2

[Wayne King]

Have you read the help for dwt2? You need to specify a wavelet name (or the filters) to use.

It's better to use wavedec2 because you can specify the level that you want.

wavedec2 uses dwt2.m internally but handles the iteration for you.

imdata = imread('ngc6543a.jpg');
[C,S] = wavedec2(imdata,3,'bior3.5');

[Pooja]

Thank you so much for your reply.Sorry for asking *how to display the decomposed image and to the coefficients.*I need to give these coefficients to encoder "The output wavelet 2-D decomposition structure [C,S] contains the wavelet decomposition vector C and the corresponding bookeeping matrix S. " I got this from matlab help.

[Wayne King]

You can extract the detail or approximation coefficients at any level with

 detcoef2() or appcoef2()

[Pooja]

how to show the image after this step [C,S] = wavedec2(imdata,3,'bior3.5');

I wanted to show the image with three level decompostion.

[Deepika]

Hello Pooja, Mr. Wayne King is right. After that you should write imshow(). Then, you will get the what you want.