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https://github.com/colindean/optar

OPTical ARchiver - highly compressed 2D barcode for paper or film archiving of digital data
https://github.com/colindean/optar

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OPTical ARchiver - highly compressed 2D barcode for paper or film archiving of digital data

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README 

        
Twibright Optar

===============



[![Build Status](https://travis-ci.org/colindean/optar.png?branch=master)](https://travis-ci.org/colindean/optar)



_**Special note:** The repository of optar at http://github.com/colindean/optar 

exists because I (@colindean) had difficulties finding the source and it seemed

to be abandoned/dormant. I've made slight improvements over time. Improvements

welcomed as pull requests._



This is a program to store data on paper using a 600 dpi black and white laser

printer and a 600+ dpi scanner.



Building

--------



You need to install [ImageMagick](https://www.imagemagick.org) so that the 

resulting .pgm image can be converted into PostScript with the right dimensions:

each pixel must be 3x3 600dpi pixels so that there is no unnecessary jitter.



Make sure you have [libpng](http://libpng.org/pub/png/) installed. You'll know

that is is installed correctly if you type `libpng-config` on the commandline, 

there's a program which prints something. Virtually all desktop Linux distros 

and every macOS system has this installed already.



Compile with



    make



Note that there may be some hardcoded configuration values that you may need to

change, for example the page size defaults to A4 instead of US Letter. Read on

to learn where to change that.



Installing locally

------------------



It's easiest to install your local build with



    sudo make install



`optar`, `unoptar`, and `pgm2ps` installed on your system in `/usr/local/bin`. 



To uninstall, run



    sudo make uninstall



Encoding (writing)

------------------



Run



    optar other_guys.ogg other_guys.ogg



which will produce files:



```

other_guys.ogg_0001.pgm

other_guys.ogg_0002.pgm

other_guys.ogg_0003.pgm

other_guys.ogg_0004.pgm

other_guys.ogg_0005.pgm

other_guys.ogg_0006.pgm

```



Now convert them into PostScript using the included pgm2ps tool:



    pgm2ps *.pgm



Print these using a 600 dpi (or greater resolution) **laser** printer. Inkjet or

dot matrix was never tested and will not probably work at the pre-defined data 

density. See "Changing the format" below.



Please note that the file will be padded by zeroes and the original length will

be lost. **Pack your data with tar if you store data that are sensitive to

this.**



Decoding (reading)

------------------



Clean and polish the scanner glass with rubbing alcohol and paper towel. Put

yellow pages on the scanner lid to get sharper picture˚. Insert the

page so that the text on the bottom is upright. Scan the pages into

PNG (not JPEG!) on 600dpi (or 1200dpi, slightly better):



```

scan_0001.png

scan_0002.png

scan_0003.png

scan_0004.png

scan_0005.png

scan_0006.png

```



Read the number sequence (format specification) from any of the papers and feed

it as 1st argument to the optar, 2nd argument is the filename part before the

underscore:



    unoptar 0-65-93-24-3-1-2-24 scan > out.ogg



Then play out.ogg with mplayer. You should get first about 41 seconds from the

Ogg Vorbis file.



˚ In the scanner I tried (Canoscan), the lid didn't seem to be heavy enough to

press the paper down completely - there were blurry spots in the picture.

Without yellow pages I got 526 reparable bad bits bad from 3.2 million. With

yellow pages the blurry spots were much sharper and I got only 261 reparably

bad bits!



Please note the data are padded with zeroes so the original information

about file length is lost. **If your data format doesn't like this then first

pack your data with `tar`.**



A4 <-> US Letter

----------------

Change the convert parameters in pgm2ps (see comments). Change XCROSSES

and YCROSSES in optar.h (see comments). Recompile. Then you can use US Letter

instead of A4.



Changing the format

-------------------

If your printer is low quality and you are getting irreparable bits, you can

try to format the media to lower capacity.  Unfortunately, setting by

commandline is not implemented yet.  Change XCROSSES and YCROSSES in optar.h to

lower values which yields bigger pixels and lower capacity per page, but higher

reliability.  Make sure they are in roughly the same proportion as before,

otherwise you get nonsquare pixels and unnecessary waste of channel capacity.



You can also change the decoding parameters in unoptar.c (look for MAGIC

CONSTANTS) in attempt to read a difficult recording: unsharp_mask,

unsharp_dist, sync_white_cut, white_cut, minmax_filter, pixel_blur, cross_trim.



Future improvement

------------------

- manpage could be written for optar and unoptar

- commandline help (-h) could be written for optar and unoptar

- the format could be made configurable. Now it's stored in the optar.h

- the magic constants could be changed by commandline options. Now they are

  stored in unoptar.c.

- Golay code decoding could be rewritten faster, using a sophisticated

  algorithm (Kasami algorithm?)

- Easy support for multiple pages per page, so it can be read by a digital

  camera. Currently it cannot since digital camera blurs at the sides of

  the picture.



Authorship and Licensing

------------------------



© GPL 2007 Karel 'Clock' Kulhavy of Twibright Labs. 



See COPYING for the text of the GPL license.



e-mail: clock (at) twibright (dot) com



Twibright Optar homepage: http://ronja.twibright.com/optar/



Improvements © 2012-2018 Colin Dean