Zebras & Lasers (PyBay 2018)

Transcript

1. Zebras and Lasers:
   A crash course on barcodes with Python
   Jonas Neubert
   3rd Annual Regional Python Conference August 16 - 19, 2018 | San Francisco, CA
   

   View Slide

2. Jonas Neubert
   Software Engineer at Zymergen
   slides: http://jonasneubert.com/talks/pybay2018.html
   twitter: @jonemo
   

   View Slide

3. From First Principles
   ʵ Barcodes Theory
   ż Barcodes with Python
   Ʉ Barcodes in The Realworld
   

   View Slide

4. View Slide

5. Barcodes Theory
   

   View Slide

6. Symbology
   - Geometric primitives (lines, circles, matrix, ...)
   - Arrangement of primitives (single row, concentric, stacked, …)
   - Symbol table (pixels → bits)
   - Encoding (bits → information)
   - Checksums and Error Correction
   Code
   - What the numbers mean (part numbers, ZIP codes, ...)
   

   View Slide

7. Code 128: Full ASCII, variable length, continuous (11,3), three character sets
   

   View Slide

8. 11 slots
   3 bars & 3 gaps per character
   Maximum Bar Size: 4 Slots
   106 Different Characters
   3 Character Sets for “Full-Ascii”
   Code 128: Full ASCII, variable length, continuous (11,3), three character sets
   

   View Slide

9. character “P”
   (0x30)
   Code 128: Full ASCII, variable length, continuous (11,3), three character sets
   

   View Slide

10. character “H”(0x28)
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

11. character “P”(0x30)
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

12. “PHP”
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

13. “PHP” cHecksUm
    (0x43)
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

14. “PHP”
    stARt coDE
    (0x68)
    STOP Code
    ..(0x70)
    cHecksUm
    (0x43)
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

15. “PHP”
    stARt coDE
    (0x68)
    STOP Code
    ..(0x70)
    cHecksUm
    (0x43)
    quiet ZonEs
    Code 128: Full ASCII, variable length, continuous (11,3), three character sets
    

    View Slide

16. Code 39: Numbers and uppercase letters (39 chars), discrete 3-of-9 2-width
    12 slots
    5 bars & 4 gaps per character
    Two distinct widths
    3 out of 9 Bars or Gaps are 2x wide
    Variable Gap between characters
    39 Different Characters: A-Z 0-9 *$/+%
    

    View Slide

17. *
    Start code ?
    Just use “*”
    STOP CODE?
    Another
    “*”
    cHecksUm optional
    *
    H
    P P
    Code 39: Numbers and uppercase letters (39 chars), discrete 3-of-9 2-width
    

    View Slide

18. Interleaved 2-of-5: Numbers only, variable length, continuous 2-of-5 2-width
    

    View Slide

19. 0
    8 8
    1
    Start
    Guard StoP Guard
    cHecksUm
    optional
    Interleaved 2-of-5: Numbers only, variable length, continuous 2-of-5 2-width
    

    View Slide

20. POSTNET: Numbers only, fixed length, clocked continuous 2-of-5, height-modulated
    USPS pre-2009
    

    View Slide

21. POSTNET: Numbers only, fixed length, clocked continuous 2-of-5, height-modulated
    USPS pre-2009
    

    View Slide

22. Start GUard
    STOP
    guarD
    cHecksUm
    9 4 1 4 3 3 0 0 8
    -
    POSTNET: Numbers only, fixed length, clocked continuous 2-of-5, height-modulated
    USPS pre-2009
    

    View Slide

23. Zielcode: Numbers only, fixed length, continuous 2-of-5 1-width
    Deutsche Post
    Source: Helmut Schraets: Meilensteine der Briefcodierung (1998).
    https://www.briefmarken-kevelaer.de/media/files/Meilensteine-Neu.pdf
    

    View Slide

24. Intelligent Mail®: Numbers only, variable length, clocked 4-state, height-modulated
    US Postal since 2009
    00-300-123456-123456789-94143-3008-00
    “Send First Class letter with no services (300) no OEL information (00) to UCSF Conference
    center (94143-3008-00) using mAILer ID 123456 and sequence number 123456789”
    

    View Slide

25. Source: USPS: Intelligent Mail Barcode 4-state Specification (2015),
    Intelligent Mail®: Numbers only, variable length, clocked 4-state, height-modulated
    US Postal since 2009
    

    View Slide

26. :CueCat: Like Code 128 but at 22.5° angle and proprietary code
    

    View Slide

27. Rule of Thumb:
    Height = 0.15 * Width
    Anonymous 1980s engineer
    pulling Number out of his Hat
    Bacon
    

    View Slide

28. Bacon & Eggs Rule of Thumb:
    Height = 0.15 * Width
    Anonymous 1980s engineer
    pulling Number out of his Hat
    

    View Slide

29. Bacon & Egg with Toast
    Rule of Thumb:
    Height = 0.15 * Width
    Anonymous 1980s engineer
    pulling Number out of his Hat
    

    View Slide

30. Code 49: Stacked linear codes, fixed length (49 chars)
    Full Breakfast with Bacon & Eggs
    and Toast & Jam
    

    View Slide

31. Code 16k: Stack of inverted Code 128 symbols, 77 chars or 154 digits
    

    View Slide

32. PDF417: “High capacity”, variable length, stack of continuous (17,4) codes
    Full Breakfast with Bacon, Baked Beans and Eggs
    and Toast or an English Muffin as a side.
    

    View Slide

33. PDF417: “High capacity”, variable length, stack of continuous (17,4) codes
    

    View Slide

34. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    PyBay
    

    View Slide

35. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    White in Top right
    means: Uses EC200
    PyBay
    Left and bottom
    guards are solid
    Top and right guards
    are clocked
    

    View Slide

36. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    White in Top right
    means: Uses EC200
    PyBay
    Left and bottom
    guards are solid
    Top and right guards
    are clocked
    

    View Slide

37. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    White in Top right
    means: Uses EC200
    PyBay
    Left and bottom
    guards are solid
    Top and right guards
    are clocked
    P
    y
    B
    P
    y
    a
    B a
    REED-SOLOMON ERROR
    CORRECTION
    PADDING
    

    View Slide

38. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    

    View Slide

39. Data Matrix: Arbitrary data, up to 1556 bytes/2335 chars/3116 digits
    

    View Slide

40. Semacode: Code for storing URLs in Datamatrix
    Source: Bernd Hopfengärtner: Hello World! (2007)
    http://hello.w0r1d.net/
    

    View Slide

41. QR: up to 7089 digits or 4296 ASCII characters or 1817 Kanji characters
    

    View Slide

42. QR: up to 7089 digits or 4296 ASCII characters or 1817 Kanji characters
    Source: Xinhua (2017)
    http://www.xinhuanet.com/photo/2017-09/14/c_1121662356_2.htm
    

    View Slide

43. Aztec:
    up to 3832 digits or
    3067 characters
    Maxicode:
    exactly 596 bits,
    hexagonal
    elements
    Grid Matrix:
    optimized for
    encoding Chinese
    characters
    Code One: First
    non-proprietary 2D
    symbology (1992)
    Micro QR:
    Variation of QR Code,
    numeric, up to 35 digits,
    single alignment mark
    ← HIBC Datamatrix:
    Variation of Datamatrix,
    up to 36 characters, used
    in medical devices
    ←
    

    View Slide

44. UPC/EAN: Numbers only, fixed length of 12 or 13 digits, continuous (7,2) 4-width
    Source: Businessweek, April 7, 1973. Available on the website of the
    ID History Museum at http://idhistory.com/ibm/Busweek1973001.pdf
    

    View Slide

45. 1D
    Interleaved 2-of-5
    Code 39
    Code 128
    :CueCat
    Bullseye
    UPC/EAN
    Stacked
    Code 49
    Code 16k
    PDF417
    Matrix
    Datamatrix
    Aztec
    Maxicode
    Grid Matrix
    Code One
    QR
    Mini QR
    POSTNET
    RM4SCC
    PostBar
    Intelligent Mail
    

    View Slide

46. 1D
    Interleaved 2-of-5
    Code 39
    Code 128
    :CueCat
    Codabar
    Code 11
    Code 93
    93i
    Channel Code
    Bullseye
    UPC-A, UPC-E
    EAN-13, EAN-8
    GS1-128
    GS1 Databar (RSS)
    Plessey Code
    Stacked
    Code 49
    Code 16k
    PDF417
    MicroPDF417
    Codablock
    SuperCode
    UltraCode
    GS1 Databar St.
    Matrix
    Datamatrix
    Aztec
    Maxicode
    Grid Matrix
    Code One
    QR
    Mini QR
    Vericode
    MiniCode
    GoCode
    POSTNET
    RM4SCC
    PostBar
    Intelligent Mail
    Data Logic
    Leitcode
    Pharmacode
    PZN
    ISBN
    Composite
    Aztec Mesas
    EAN.UCC
    EAN-14 Comp.
    RSS-14 Comp.
    RSS-14 St. Comp.
    

    View Slide

47. Interleaved 2 of 5
    Code 128
    Code 128
    M
    axicode
    M
    icro
    QR
    Code 39
    Code 39
    Code 128
    Code 39
    

    View Slide

48. How to pick a symbology?
    Does your application
    dictate a specific
    symbology?
    Continue listening to this
    presentation.
    Use the symbology
    dictated by your
    application.
    Yes
    No
    

    View Slide

49. Reader Technology
    Really bright lamps
    ✍ Wands
    ɾ Laser
    ɑ Imaging
    

    View Slide

50. Reader Technology
    Really bright lamps
    ✍ Wands
    ɾ Laser
    ɑ Imaging
    Photos:
    “ACI plate on an IANR hopper” by Feddacheenee on Wikimedia Commons.
    https://commons.wikimedia.org/wiki/File:ACI_plate.jpg
    “Petrified Forest, Flora, Summer 2010” Quinn Rossi on flickr, Licensed under CC BY 2.0.
    https://www.flickr.com/photos/theeskimo/4898894840/
    

    View Slide

51. Reader Technology
    Really bright lamps
    ✍ Wands
    ɾ Laser
    ɑ Imaging
    Photo:
    “Barcodelesestift mit Leseeinheit” by I,Nightflyer on Wikimedia.de under CC BY-SA 3.0
    https://de.wikipedia.org/wiki/Barcodeleseger%C3%A4t#/media/File:Barcodelesestift.jpg
    

    View Slide

52. Reader Technology
    Really bright lamps
    ✍ Wands
    ɾ Laser
    ɑ Imaging
    

    View Slide

53. Reader Technology
    Really bright lamps
    ✍ Wands
    ɾ Laser
    ɑ Imaging
    Photo: “Swap Paper for Mobile Boarding Passes“ by City of Mc Allen.
    

    View Slide

54. View Slide

55. View Slide

56. Printing Technology
    

    View Slide

57. Direct Parts Marking: Permanently marking a piece by punching, etching, laser, etc.
    “Printing” Technology
    

    View Slide

58. “Printing” Technology
    Otolith Marking: Information stored in fish bones for fishery management
    Photo: randychiu on flickr, Licensed under CC BY 2.0.
    https://www.flickr.com/photos/randychiu/4817651586/
    

    View Slide

59. Barcodes with Python
    

    View Slide

60. Generating Barcodes
    >>> import barcode
    >>> bc = barcode.get_barcode('code39', 'PYBAY2018')
    >>> bc.save('mybc')
    'mybc.svg'
    pip install python-barcode
    

    View Slide

61. Generating Barcodes
    >>> import barcode
    >>> barcode.generate('code39', 'PYBAY2018', output='mybc')
    'mybc.svg'
    pip install viivakoodi
    

    View Slide

62. Generating Barcodes
    >>> from pubcode import Code128
    >>> bc = Code128('PyBay2018', charset='B')
    >>> bc.bars
    '21121431312121214113112312112421214122321112312212322131122
    >>> bc.image(height=50).save('mybarcode.png')
    MissingDependencyError: PIL module is required to use image
    pip install PubCode
    

    View Slide

63. Generating Barcodes
    >>> from pubcode import Code128
    >>> bc = Code128('PyBay2018', charset='B')
    >>> bc.bars
    '21121431312121214113112312112421214122321112312212322131122
    >>> bc.image(height=50).save('mybarcode.png')
    pip install PubCode pillow
    

    View Slide

64. Generating Barcodes
    import pdf417gen, this
    data = pdf417gen.encode(this.s)
    image = pdf417gen.render_image(data)
    image.save('mybarcode.png')
    pip install pdf417gen
    

    View Slide

65. ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓ ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓ ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓ ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    ✓
    Generating Barcodes
    treepoem
    pyBarcode
    ↳ python-barcode
    ↳ viivakoodi
    ↳ steenzout.barcode
    ↳ reBarcode
    pyStrich (fork of huBarcode)
    qrcode
    PyQRCode
    segno
    pdf417gen
    code128
    PubCode
    candybar
    License
    MIT
    MIT
    MIT
    MIT
    MIT
    MIT
    Apache
    BSD
    BSD
    BSD
    MIT
    LGPL
    MIT
    Apache
    UPC-A
    EAN
    ISBN
    PZN
    I. 2 of 5
    Code 39
    Code 93
    Code 128
    Data Matrix
    PDF417
    QR
    Micro QR
    ★
    123
    N/A
    17
    28
    5
    0
    N/A
    1,481
    204
    18
    13
    N/A
    1
    2
    Latest
    release
    June 2018
    July 2013*
    June 2018
    Nov 2014
    Jan2017
    Oct 2017
    July 2016
    Mar 2018
    June 2016
    Feb 2018
    May 2017
    Jan 2015
    Aug 2015
    Aug 2016
    Output
    1: SVG
    2: pillow
    3: pypng
    []: optional
    2
    1, [2]
    1, [2]
    1, [2]
    1, [2]
    1, [2]
    2
    1, 3, [2]
    1, 3
    2
    1, [2]
    2
    2
    ✓
    Aztec
    various formats,
    no external dep.
    

    View Slide

66. Generating Barcodes
    Easy to install, support for common symbologies:
    python-barcode
    license: MIT, last updated: June 2018
    https://pypi.org/project/python-barcode/
    Most feature rich tool:
    Treepoem (uses BWIPP, requires Postscript)
    license: MIT, last updated: Aug 2018
    https://pypi.org/project/treepoem/
    Symbology specific libraries:
    Segno (QR, Micro QR), pdf417gen, libdmtx (Datamatrix), PubCode (Code 128)
    

    View Slide

67. Reading Barcodes with Python
    

    View Slide

68. Don’t read barcodes with Python
    Use purpose-built hardware
    whenever possible. These
    can optimize every step of
    the process going from light
    to data.
    Photos: “Symbol Motorola” by Lost Parcels on flickr, licensed under CC BY 2.0,
    https://www.flickr.com/photos/lostparcels/31046764866/. By HP APJ on flickr, licensed
    under CC BY-NC-ND 2.0, https://www.flickr.com/photos/personalagain/5444387315/
    

    View Slide

69. Reading Barcodes with Python
    Pick your poison:
    zbar
    C/C++ library
    EAN-8/13, UPC-A/E, EAN-8, Interleaved 2 of 5,
    Code 39, Code 128, QR
    (not documented: Codabar, Code 93, PDF417)
    license: LGPL 2.0, last updated: Oct 2009
    https://sourceforge.net/projects/zbar/
    ZXing
    Java library (and C++ rewrite/port/fork)
    same as zbar, plus: Codabar, Code 93, ITF, Data
    Matrix, Aztec, PDF417, Maxicode, GS1 Databar
    (and various codes using these symbologies)
    license: MIT, last updated: Aug 2018
    https://github.com/zxing/zxing (Java)
    https://github.com/glassechidna/zxing-cpp (C++)
    libdmtx
    C/C++ library, .NET fork, Datamatrix symbology only
    license: LGPL 2.0, last updated: unclear
    https://sourceforge.net/projects/libdmtx/, https://github.com/dmtx,
    https://sourceforge.net/projects/datamatrixnet/
    

    View Slide

70. “The Original”
    Last updated 2009
    Python 2 only
    Actively maintained
    Python 2 and Python 3
    Actively maintained
    Advertises easy Windows
    installation
    

    View Slide

71. There exists an sparsely
    maintained C++ rewrite/port/fork
    of ZXing (). This wraps that.
    https://github.com/glassechidna/zxing-cpp
    https://github.com/lubo/zxinglight
    - Setup.py downloads .jars
    - uses subprocess.Popen()
    Python 3 only
    

    View Slide

72. ZXing example
    >>> import zxing
    >>> reader = zxing.BarCodeReader()
    >>> barcode = reader.decode("boardingpass.png")
    BarCode('420941079374889676090739719680',
    '420941079374889676090739719680', 'CODE_128', 'TEXT',
    [(37.5, 96.0), (805.0, 96.0)])
    pip install zxing
    

    View Slide

73. Reading for Ȑ :
    Commercial SDKs
    Python support advertised
    Scandit (C)
    https://www.scandit.com/products/barcode-scanner/barcod
    e-scanner-details/
    Cognex ManateeWorks
    https://manateeworks.com/barcode-scanner-sdk
    Vintasoft (.NET)
    http://www.vintasoft.com/vsbarcode-dotnet-index.html
    Leadtools Barcode SDK (Java, C, .NET Core)
    https://www.leadtools.com/sdk/barcode
    DTKSoft Barcode SDK (Windows only)
    https://www.dtksoft.com/?p=barcodesdk
    Sension (C++)
    https://www.sensionweb.com/codemax-barcode-sdk
    Python support advertised
    Dynamsoft Barcode Reader
    https://www.dynamsoft.com/
    https://pypi.org/project/dbr/
    Matrox Imaging Library
    https://www.matrox.com/imaging/en/products/software/mil/
    (Python wrapper available as “update”)
    NO endorsement is implied.
    Do yoUR own rESEarch!
    

    View Slide

74. View Slide

75. View Slide

76. Barcodes in the Realworld
    

    View Slide

77. Barcodes as real-world Browser Cookies
    

    View Slide

78. Barcodes as Information
    Photo: “Heinz QR porn code too saucy for ketchup customer”, BBC, Jun
    https://www.bbc.com/news/technology-33200142
    

    View Slide

79. Barcodes as Passwords (spoiler: don’t do it)
    

    View Slide

80. Barcodes as Passwords (spoiler: don’t do it)
    >>> barcode = reader.decode("boardingpass.png").raw
    'M1NEUBERT/JONAS EP8LD5W SFOSANUA 1900 034Y029D0071 15D>5180
    W8034BUA 2A01123810700013 UA UA GV444737 N*30600 05
    ^QO6IGQATNXzqrr57ZahTjZGbeLkuah2ZCvlKPeBBodwewJDZWTitJftePwRGUZs
    F7yCngxRxKj9x9MtIAbgLE21TueaF4GIT7QU'
    

    View Slide

81. Barcodes as Passwords (spoiler: don’t do it)
    

    View Slide

82. RTFM (part 1)
    Understand the hardware you are using
    A barcode reader with factory settings is like a Windows PC without a firewall
    

    View Slide

83. RTFM (part 2)
    Understand the symbology you are using
    Example: With the Interleaved 2-of-5 symbology makes valid partial scans very
    likely, only use with fixed length content
    I AM A RED STICKER
    THAT BREAKS
    YOUR BARCODE
    “4321”
    “0987654321”
    

    View Slide

84. RTFM (part 3)
    Understand the code you are using
    Example: Google Chrome “crashes” when scanning a product code into a textbox
    Here’s why:
    - Product code is a GS1 Datamatrix code
    - GS1 Datamatrix specifies “FNC1” character as separator
    - Code 128 maps “FNC1” to 0x64
    - My barcode reader decides to communicate 0x64 as F8 key
    - In Chrome developer tools “F8” means: Stop code execution
    

    View Slide

85. Tips for working with barcodes
    - “Outsource” the decoding if you can
    - Use a symbology that is right and safe for your data type
    - Configure your reader hardware
    - Limit the symbologies accepted to those you actually need
    - Disable reader configuration through barcodes
    - Validate input as if it was user input (because it is)
    - Validate that only the characters or numbers you expect are used
    - Check length of data (most symbologies are variable length)
    - Protect against Little Bobby Barcodes injection attacks
    - If your software hands out barcodes, treat them like browser cookies
    - Never include secrets in barcodes
    

    View Slide

86. My last slide
    What’s the URL for these slides again?
    http://jonasneubert.com/talks/pybay2018.html
    Want to work with me?
    https://www.zymergen.com/careers/
    Watching this on Youtube?
    The best ways to reach me are Twitter (@jonemo)
    and email (jn@jonasneubert.com)
    

    View Slide

87. Books
    Roger C. Palmer: The Bar Code Book: A Comprehensive Guid To Reading, Printing, Specifying,
    Evaluating, And Using Bar Code and Other Machine-Readable Symbols, 5th ed., Trafford Pub. 2007
    John Berry: The Secret Life of Bar Codes, Wirksworth Books, 2013
    Gavin Weightman: Eureka: How Invention Happens, Yale University Press, 2017. Excerpt available at
    https://www.smithsonianmag.com/innovation/history-bar-code-180956704/
    —
    I didn’t read the following but came across references to them during my research for this presentation:
    Ben Nelson: Punched Cards to Barcodes: A 200 Year Journey with Descriptions of over 260 Cods,
    Helmers Publishing, 1997.
    Stephen A. Brown: Revolution at the Checkout Counter: The Explosion of the Bar Code, Wertheim
    Publications in Industrial Relations, 1997.
    Bill Selmeier: Spreading the Barcode, Lulu.com, 2010.
    George J. Laurer: Engineering Was Fun, 3rd ed., Lulu.com, 2012.
    

    View Slide

88. Articles
    Katie Mingle: Barcodes. 99 Percent Invisible. 2014.
    https://99percentinvisible.org/episode/barcodes/
    Ernie Smith: Right Track, Wrong Station, Tedium. 2017.
    https://tedium.co/2017/09/05/kartrak-railroad-barcode-history/
    Ernie Smith: Switching Labels, Tedium. 2017.
    https://tedium.co/2017/11/13/retail-theft-ticket-switching/
    Ernie Smith: When Tech Hit Retail, Tedium. 2017.
    https://tedium.co/2017/07/20/point-of-sale-retail-history/
    Larry Silverman: Barcodes, A Brief History, TrackAbout, 2015.
    https://corp.trackabout.com/barcodes-brief-history
    Brian Krebs: Why It’s Still A Bad Idea to Post or Trash Your Airline Boarding Pass, 2017.
    https://krebsonsecurity.com/2017/08/why-its-still-a-bad-idea-to-post-or-trash-your-airline-boarding-pass/
    Jonas Neubert: Intro to Barcode Readers, 2017.
    http://jonemo.github.io/neubertify/2017/02/26/intro-to-barcode-readers/
    Shaun Ewing: What’s contained in a boarding pass barcode, 2011.
    https://shaun.net/notes/whats-contained-in-a-boarding-pass-barcode/
    

    View Slide

89. Videos & Talks
    Barcode in Black and White, Groupe Média TFO.
    https://www.youtube.com/watch?v=FXPSd5o0GeU (published to Youtube by OCR Canada Ltd.)
    “FX” Felix Lindner: Toying with Barcodes, DEFCON 16 (2008).
    https://www.youtube.com/watch?v=qT_gwl1drhc
    Karsten Nohl, Nemanja Nikodijevic: Where in the World Is Carmen San Diego, Becoming a Secret Travel
    Agent, 33c3 (2016). https://media.ccc.de/v/33c3-7964-where_in_the_world_is_carmen_sandiego
    Karina Ruzinov: Shipping secret messages through barcodes, PyCascades 2018.
    https://www.youtube.com/watch?v=01E5exVatGA
    

    View Slide

90. Online Resources (besides Wikipedia)
    Russ Adams: Barcode 1. http://www.adams1.com/
    Retail Identification History Museum. http://www.idhistory.com/
    Egoditor UG: http://www.barcode-generator.org/ (scroll down past the generator for content)
    

    View Slide

91. The Original Barcode Patent
    US2612994A: Classifying apparatus and method, 1949, Norman J Woodland, Silver Bernard (Drexel
    University)
    Otolith Marking (Barcodes in Fish Bones)
    Volk, Schroder, Grimm, Ackley: Use Of A Bar Code Symbology to Produce Multiple Thermally Induced
    Otolith Marks, Transactions of the American Fisheries Society, vol. 123, is. 5, pp. 811-816 (1994).
    Volk, Schroder, Grimm: Otolith thermal marking, Fisheries Research, vol. 43, is. 1-3, pp. 205-219 (1999).
    Helmut Schraets: Meilensteine der Briefcodierung (1998).
    https://www.briefmarken-kevelaer.de/media/files/Meilensteine-Neu.pdf
    USPS: Intelligent Mail Barcode 4-state Specification (2015).
    https://ribbs.usps.gov/intelligentmail_mailpieces/documents/tech_guides/USPSB3200IntelligentMailBarco
    de4State.pdf
    DNA Bardcoding
    https://en.wikipedia.org/wiki/DNA_barcoding
    

    View Slide

92. Image Attributions
    Zebra by m. turan ercan from the Noun Project: https://thenounproject.com/term/zebra/67862/
    

    View Slide