i am working on Image Compression Using Run Length Encoding

am getting error in scanning in zigzag the error is as follows

Undefined function or variable 'toZigzag'.

Error in rlc_haar (line 21)

ImageArray=toZigzag(QuantizedImage);

plese help me

%%Matlab code for Image Compression Using Run Length Encoding

      clc;
      clear;
      close all;
      %%Set Quantization Parameter
      quantizedvalue=10;
      %%Read Input Image
      InputImage=imread('cameraman.tif');
      [row col p]=size(InputImage);

      %%Wavelet Decomposition 
      [LL LH HL HH]=dwt2(InputImage,'haar'); 
      WaveletDecomposeImage=[LL,LH;HL,HH]; 
      imshow(WaveletDecomposeImage,[]);

      %uniform quantization
      QuantizedImage= WaveletDecomposeImage/quantizedvalue;
      QuantizedImage= round(QuantizedImage);

      % Convert the Two dimensional Image to a one dimensional Array using ZigZag Scanning
      ImageArray=toZigzag(QuantizedImage);

      %%Run Length Encoding
      j=1;
      a=length(ImageArray);
      count=0;
      for n=1:a
       b=ImageArray(n);
       if n==a
       count=count+1;
       c(j)=count;
       s(j)=ImageArray(n);
       elseif ImageArray(n)==ImageArray(n+1)
       count=count+1;
       elseif ImageArray(n)==b
       count=count+1;
       c(j)=count;
       s(j)=ImageArray(n);
       j=j+1;
       count=0;
       end
      end

      %%Calculation Bit Cost

      InputBitcost=row*col*8;
      InputBitcost=(InputBitcost);
      c1=length(c);
      s1=length(s);
      OutputBitcost= (c1*8)+(s1*8);
      OutputBitcost=(OutputBitcost);

      %%Run Length Decoding g=length(s);
      j=1;
      l=1;
      for i=1:g
       v(l)=s(j);
       if c(j)~=0
       w=l+c(j)-1;
       for p=l:w
       v(l)=s(j);
       l=l+1;
       end
       end
       j=j+1;
      end

      ReconstructedImageArray=v;

      %%Inverse ZigZag
      ReconstructedImage=invZigzag(ReconstructedImageArray)

      %%Inverse Quantization
      ReconstructedImage=ReconstructedImage*quantizedvalue;

[gowtham munuswami reddy]

can u do this code by using threshloding and RLC

[Walter Roberson]

Yes, it already does thresholding and Run Length Coding. The thresholding is the quantization step. The Run Length Encoding has a block of commented code right there.

[karthika]

So can't we apply zigzag scanning in rle??

[Walter Roberson]

@karthika

Sure, you can combine zigzag scanning with RLE. The resulting code would be unclear and probably would be difficult to maintain. It would probably be much more effective to have a zigzag scan function separate from the RLE function.

Answer 1

[Walter Roberson]

That code is from https://www.pantechsolutions.net/image-processing-projects/image-compression-using-run-length-encoding and has been posted without attribution.

The complete code is being sold for 2000 rupees. It is not our place to duplicate commercial code for free.

Code for RLE encoding with zigzag scan has been posted a few times on MATLAB Answers -- zigzag scan is used by JPEG encoding, so there have been a number of posts of the code for that.

[juveria fatima]

can yoy please provide the link of zigzag scan used by jpeg encoding

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/390182-how-to-convert-the-two-dimensional-image-to-a-one-dimensional-array-using-zigzag-scanning#answer_311740

https://www.google.com/search?q=site%3Awww.mathworks.com%2Fmatlabcentral%2FAnswers+zig-zag+jpeg&ie=utf-8&oe=utf-8