How to compress a location map using JBig compression?

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function [y,nbr_bits] = perform_jbig_coding(x)
% perform_jbig_coding - perform binary image coding
%
% [y,nbr_bits] = perform_jbig_coding(x);
%
% It requires pbmtojbg and jbgtopbm executable.
%
% Copyright (c) 2006 Gabriel Peyr
name_pbm = 'b.pbm';
name_jbg = 'c.jbg';
if size(x,1)>1 && size(x,2)>1
% forward transform
% save as pbm
imwrite(rescale(x), name_pbm, 'pbm');
% convert to jgib
!pbmtojbg tmp.pbm tmp.jbg
% read jbig file
fid = fopen(name_jbg);
if fid<0
error('Unable to open Jbig file.');
end
[y,cnt] = fread(fid, Inf);
fclose(fid);
nbr_bits = length(y)*8;
% remove tmp files
!del tmp.jbg
!del tmp.pbm
else
% backward transform
fid = fopen(name_jbg, 'wb');
if fid<0
error('Unable to open Jbig file.');
end
fwrite(fid, x);
fclose(fid);
% convert to pbm
!jbgtopbm tmp.jbg tmp.pbm
% read pbm
y = imread(name_pbm);
% remove tmp files
!del tmp.jbg
!del tmp.pbm
nbr_bits = -1;
end
Actually, I find this code in matlab. But I don't understand why two ".pbm" and ".jbg" are needed. I have only one location map(.pbm) to compress. As I am very new to programming, it is really hard to understand. Please help me.

Answers (3)

Walter Roberson
Walter Roberson on 26 Sep 2016
The code does not do the JBIG compression in MATLAB. Instead it calls upon an external program to do the work. That external program happens to be able to handle PBM files and convert them to JBIG files, so the image is saved to a temporary .pbm and converted to .jbg . The file is then read in so that the result of the conversion is in memory, and the two temporary files are discarded.
The code also handles the other direction, converting binary data representing JBIG into an image. It does that by writing the binary data out as a .jbg file, and using an external program to convert the .jbg file to .pbm and then reading the .pbm .
  2 Comments
Walter Roberson
Walter Roberson on 26 Sep 2016
You can get http://www.cl.cam.ac.uk/~mgk25/jbigkit/ and use calllib() to make calls into it. It appears that this is the origin of the PBM to JBIG program.
The algorithm looks like it is not trivial, and the list of (expired) patents is surprisingly long, suggesting that it is not as simple as it sounds at first. I would not recommend implementing in MATLAB unless you are being required to by someone.

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Manikandan VM
Manikandan VM on 19 Mar 2017
I am also looking for the usage of JBIG2 in matlab. JBIG c code is already obtained from http://www.cl.cam.ac.uk/~mgk25/jbigkit/. But how to make use of it in matlab??
Let me know Mr. Aarach Sap solved the issue or not??

Shounak Shastri
Shounak Shastri on 27 Mar 2018
Download the toolbox and paste it in your Matlab folder. Make sure it is added to your current working path.
Open the compile_mex.m file and comment lines 8-58 and 75-80. Execute the file.
Once this is dene, the function should be usable.
  1 Comment
Walter Roberson
Walter Roberson on 27 Mar 2018
That appears to be about jpeg2000 rather than about jbig?

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