image compression using dct,zigzag scan and runlength coding.

hello, I am trying to compress an image by applying dct, zigzag scan and run length coding. but I am stuck at zigzag coding.so can anybody tell me that how to apply zigzag scan now..here is my code till quantization.

 clc;
I = imread('cameraman.tif');
I = im2double(I);
T= dctmtx(8);
B = blkproc(I,[8 8],'P1*x*P2',T,T');
%fun=@dct2;
%B = blkproc(A,[8 8],fun);
q= [16 11 10 16 24 40 51 61;
    12 12 14 19 26 58 60 55;
    14 13 16 24 40 57 69 56;
    14 17 22 29 51 87 80 62;
    18 22 37 56 68 109 103 77;
    24 35 55 64 81 104 113 92;
    49 64 78 87 103 121 120 101;
    72 92 95 98 112 100 103 99]/255;
B2= blkproc(B,[8 8],'round(x./P1).*P1',q);
imshow(I), figure, imshow(B), figure, imshow(B2);

[Walter Roberson]

http://www.mathworks.co.uk/matlabcentral/answers/55717-jpeg-image-compression-using-huffman-encoding-and-decoding#comment_115982

[Urmila]

Thank you sir.. I have written the following code according to your suggestion. sir can you tell me that whether I am going in right direction? because i am not getting inverse of run length code..here is my code;

clc;
A = im2double(imread('cameraman.tif'));
T= dctmtx(8);
B = blkproc(A,[8 8],'P1*x*P2',T,T');
q= [16 11 10 16 24 40 51 61;
    12 12 14 19 26 58 60 55;
    14 13 16 24 40 57 69 56;
    14 17 22 29 51 87 80 62;
    18 22 37 56 68 109 103 77;
    24 35 55 64 81 104 113 92;
    49 64 78 87 103 121 120 101;
    72 92 95 98 112 100 103 99]/255;
B2= blkproc(B,[8 8],'round(x ./P1).*P1',q);
imshow(B2)
[M N]=size(B2)
fun=zigzag(B2)
fun=round(fun);
out=rle(fun);
in=irle(out);
in1=izigzag(in,M,N);

[Walter Roberson]

Looks plausible. We would need to see your rle and irle to check about why you are not getting a proper inverse.

[Urmila]

hello sir,i have used rle & irle functions that are as followings:

function:

 function Xrle=rle(XZv)
 L=length(XZv);
 j=1;
 k=1;
 i=1;
 while i<2*L
    comp=1;
    for j=j:L
        if j==L 
            break
        end;  
         if XZv(j)==XZv(j+1)
            comp=comp+1;
        else
            break
        end;
    end;
        Xrle(k+1)=comp;
        Xrle(k)=XZv(j);
        if j==L & XZv(j-1)==XZv(j) 
            break
        end;  
        i=i+1;
        k=k+2;
        j=j+1;
        if j==L 
            if mod(L,2)==0 
            Xrle(k+1)=1;
            Xrle(k)=XZv(j);
            else
            Xrle(k+1)=1;    
            Xrle(k)=XZv(j);
                       end;
             break
        end;
    end;

and irle function:

 function XZv=irle(x)
 L=length(x);
 s=1;
 k=1;
 i=1;
 while i<=L
    while s<=x(i+1)
        XZv(k)=x(i);
        s=s+1;
        k=k+1;
    end;
    i=i+2;
    s=1;
 end;

[sonam chhikara]

what is P1,P2 and X in your code?

[Walter Roberson]

P1 will be T, P2 will be T' and x will be the data.

This code was designed using the blkproc() routine that was obsolete for several years before the code was posted.

Answer 1

[Paula Souza]

Olá, como salvo os dados comprimidos pelo RLC no matlab?

[Walter Roberson]

Approximate translation:

Hello, how to save compressed data by Run Length Coding in matlab?