Jump to content

OCR-A

From Wikipedia, the free encyclopedia
(Redirected from OCR A Extended)
OCR-A
CategorySans-serif
Designer(s)American Type Founders
Commissioned byAmerican National Standards Institute
Date released1968[1]
VariationsOCR-A Extended
Sample

OCR-A is a font issued in 1966[2] and first implemented in 1968.[3] A special font was needed in the early days of computer optical character recognition, when there was a need for a font that could be recognized not only by the computers of that day, but also by humans.[4] OCR-A uses simple, thick strokes to form recognizable characters.[5] The font is monospaced (fixed-width), with the printer required to place glyphs 0.254 cm (0.10 inch) apart, and the reader required to accept any spacing between 0.2286 cm (0.09 inch) and 0.4572 cm (0.18 inch).

Standardization

[edit]

The OCR-A font was standardized by the American National Standards Institute (ANSI) as ANSI X3.17-1981. X3.4 has since become the INCITS and the OCR-A standard is now called ISO 1073-1:1976.

Implementations

[edit]

In 1968, American Type Founders produced OCR-A, one of the first optical character recognition typefaces to meet the criteria set by the U.S. Bureau of Standards. The design is simple so that it can be easily read by a machine, but it is more difficult for the human eye to read.[3]

As metal type gave way to computer-based typesetting, Tor Lillqvist used Metafont to describe the OCR-A font.[when?] That definition was subsequently improved by Richard B. Wales. Their work is available from CTAN.[6]

To make the free version of the font more accessible to users of Microsoft Windows, John Sauter converted the Metafont definitions to TrueType using potrace and FontForge in 2004.[7] In 2007, Gürkan Sengün created a Debian package from this implementation.[8] In 2008. Luc Devroye corrected the vertical positioning in John Sauter's implementation, and fixed the name of lower case z.[9]

Independently, Matthew Skala[10] used mftrace[11] to convert the Metafont definitions to TrueType format in 2006. In 2011 he released a new version created by rewriting the Metafont definitions to work with METATYPE1, generating outlines directly without an intermediate tracing step. On September 27, 2012, he updated his implementation to version 0.2.[12]

In addition to these free implementations of OCR-A, there are also implementations sold by several vendors. As a joke, Tobias Frere-Jones in 1995 created Estupido-Espezial, a redesign with swashes and a long s. It was used in a "technology"-themed section of Rolling Stone.[13][14]

Maxitype designed the OCR-X typeface—based on the OCR-A typeface with OpenType features, alien/technology-themed dingbats and available in six weights (Thin, Light, Regular, Medium, Bold, Black).[15]

Use

[edit]
OCR-A on a German bank check. The ⑂, ⑀ and ⑁ characters are used to delimit particular fields in the machine-readable line (shown here partially redacted).

Although optical character recognition technology has advanced to the point where such simple fonts are no longer necessary,[16] the OCR-A font has remained in use. Its usage remains widespread in the encoding of checks around the world. Some lock box companies still insist that the account number and amount owed on a bill return form be printed in OCR-A.[17] Also, because of its unusual look, it is sometimes used in advertising and display graphics.

Notably, it is used for the subtitles in films and television series such as Blacklist and for the main titles in The Pretender. Additionally, OCR-A is used[how?] for the films Crimson Tide and 13 Hours: The Secret Soldiers of Benghazi.

Code points

[edit]

A font is a set of character shapes, or glyphs. For a computer to use a font, each glyph must be assigned a code point in a character set. When OCR-A was being standardized the usual character coding was the American Standard Code for Information Interchange or ASCII. Not all of the glyphs of OCR-A fit into ASCII, and for five of the characters there were alternate glyphs, which might have suggested the need for a second font. However, for convenience and efficiency all of the glyphs were expected to be accessible in a single font using ASCII coding, with the additional characters placed at coding points that would otherwise have been unused.

The modern descendant of ASCII is Unicode, also known as ISO 10646. Unicode contains ASCII and has special provisions for OCR characters, so some implementations of OCR-A have looked to Unicode for guidance on character code assignments.

Pre-Unicode standard representation

[edit]

The ISO standard ISO 2033:1983, and the corresponding Japanese Industrial Standard JIS X 9010:1984 (originally JIS C 6229-1984), define character encodings for OCR-A, OCR-B and E-13B. For OCR-A, they define a modified 7-bit ASCII set (also known by its ISO-IR number ISO-IR-91) including only uppercase letters, digits, a subset of the punctuation and symbols, and some additional symbols.[18] Codes which are redefined relative to ASCII, as opposed to simply omitted, are listed below:

Character Image Location In ASCII Comments
£ Pound Sign 0x23 # Matches BS 4730, the United Kingdom variant of ISO 646.[19]
{ Left Curly Bracket 0x28 ( Character name is still "LEFT PARENTHESIS", despite showing a brace. Usual left brace ASCII code 0x7B is omitted.[18]
} Right Curly Bracket 0x29 ) Character name is still "RIGHT PARENTHESIS", despite showing a brace. Usual right brace ASCII code 0x7D is omitted.[18]
⑀ OCR Hook 0x3C <
⑁ OCR Chair 0x3E >
¥ Yen Sign 0x5C \ Matches JIS X 0201. Included in JIS X 9010, but omitted by ISO 2033.[18]
⑂ OCR Fork 0x5D ]

Additionally, the long vertical mark (Long Vertical Mark) is encoded at 0x7C, corresponding to the ASCII vertical bar (|).[18]

Dedicated OCR-A characters in Unicode

[edit]
Main article: Optical Character Recognition (Unicode block)

The following characters have been defined for control purposes and are now in the "Optical Character Recognition" Unicode range 2440–245F:

Dedicated OCR-A code points based on ASCII and Unicode[20]
Name Image Text Unicode
OCR Hook OCR Hook ⑀ U+2440
OCR Chair OCR Chair ⑁ U+2441
OCR Fork OCR Fork ⑂ U+2442
OCR Inverted fork ⑃ ⑃ U+2443
OCR Belt buckle ⑄ ⑄ U+2444
OCR Bow tie ⑅ ⑅ U+2445

Space, digits, and unaccented letters

[edit]
OCR-A digits
OCR-A unaccented capital letters
OCR-A unaccented small letters

All implementations of OCR-A use U+0020 for space, U+0030 through U+0039 for the decimal digits, U+0041 through U+005A for the unaccented upper case letters, and U+0061 through U+007A for the unaccented lower case letters.

Regular characters

[edit]

In addition to the digits and unaccented letters, many of the characters of OCR-A have obvious code points in ASCII. Of those that do not, most, including all of OCR-A's accented letters, have obvious code points in Unicode.

Additional OCR-A code points based on ASCII and Unicode
Name Glyph Unicode
Exclamation Mark Exclamation Mark U+0021
Quotation Mark Quotation Mark U+0022
Number Sign Number Sign U+0023
Dollar Sign Dollar Sign U+0024
Percent Sign Percent Sign U+0025
Ampersand Ampersand U+0026
Apostrophe Apostrophe U+0027
Left Parenthesis Left Parenthesis U+0028
Right Parenthesis Right Parenthesis U+0029
Asterisk Asterisk U+002A
Plus Sign Plus Sign U+002B
Comma Comma U+002C
Hyphen-Minus Hyphen-Minus U+002D
Full Stop (Period) Full Stop (Period) U+002E
Solidus (Slash) Solidus (Slash) U+002F
Colon Colon U+003A
Semicolon Semicolon U+003B
Less-Than Sign Less-Than Sign U+003C
Equals Sign Equals Sign U+003D
Greater-Than Sign Greater-Than Sign U+003E
Question Mark Question Mark U+003F
Commercial At Commercial At U+0040
Left Square Bracket Left Square Bracket U+005B
Reverse Solidus (Backslash) Reverse Solidus U+005C
Right Square Bracket Right Square Bracket U+005D
Circumflex Accent Circumflex Accent U+005E
Left Curly Bracket Left Curly Bracket U+007B
Right Curly Bracket Right Curly Bracket U+007D
Pound Sign (Sterling) Pound Sign U+00A3
Yen Sign Yen Sign U+00A5
Latin Capital Letter A with Dieresis Latin Capital Letter A with Dieresis U+00C4
Latin Capital Letter A with Ring Above Latin Capital Letter A with Ring Above U+00C5
Latin Capital Letter AE Latin Capital Letter AE U+00C6
Latin Capital Letter N with Tilde Latin Capital Letter N with Tilde U+00D1
Latin Capital Letter O with Dieresis Latin Capital Letter O with Dieresis U+00D6
Latin Capital Letter O with Stroke Latin Capital Letter O with Stroke U+00D8
Latin Capital Letter U with Dieresis Latin Capital Letter U with Dieresis U+00DC

Remaining characters

[edit]

Linotype[21] coded the remaining characters of OCR-A as follows:

Additional OCR-A Characters
Name Glyph Unicode Unicode Name
Long Vertical Mark Long Vertical Mark U+007C Vertical Line

Additional characters

[edit]

The fonts that descend from the work of Tor Lillqvist and Richard B. Wales define four characters not in OCR-A to fill out the ASCII character set. These shapes use the same style as the OCR-A character shapes. They are:

Additional ASCII characters
Name Glyph Unicode
Low Line Low Line U+005F
Grave Accent Grave Accent U+0060
Vertical Line Vertical Line U+007C
Tilde Tilde U+007E

Linotype also defines additional characters.[22]

Exceptions

[edit]

Some implementations do not use the above code point assignments for some characters.

PrecisionID

[edit]

The PrecisionID implementation of OCR-A has the following non-standard code points:[23]

  • OCR Hook at U+007E
  • OCR Chair at U+00C1
  • OCR Fork at U+00C2
  • Euro Sign at U+0080

Barcodesoft

[edit]

The Barcodesoft implementation of OCR-A has the following non-standard code points:[24][25]

  • OCR Hook at U+0060
  • OCR Chair at U+007E
  • OCR Fork at U+005F
  • Long Vertical Mark at U+007C (agrees with Linotype)
  • Character Erase at U+0008

Morovia

[edit]

The Morovia implementation of OCR-A has the following non-standard code points:[26]

  • OCR Hook at U+007E (agrees with PrecisionID)
  • OCR Chair at U+00F0
  • OCR Fork at U+005F (agrees with Barcodesoft)
  • Long Vertical Mark at U+007C (agrees with Linotype)

IDAutomation

[edit]

The IDAutomation implementation of OCR-A has the following non-standard code points:[27]

  • OCR Hook at U+007E (agrees with PrecisionID)
  • OCR Chair at U+00C1 (agrees with PrecisionID)
  • OCR Fork at U+00C2 (agrees with PrecisionID)
  • OCR Belt Buckle at U+00C3

Sellers of font standards

[edit]

See also

[edit]

Notes

[edit]
  1. ^ Background on the OCR-A font from Adobe
  2. ^ National Institute of Standards and Technology (1981). American National Standard Character Set for Optical Character Recognition (OCR-A) (PDF). ANSI X3.17-1981. American National Standards Institute, Inc. p. 3. The OCR-A character set for optical character recognition was first developed in the United States in 1961 as a numeric font only. In 1966 an alphanumeric font which contained 57 characters, including the existing numeric font, 4 abstract characters, and only capital letters, was issued. The revised standard was entitled American National Standard Character Set for Optical Character Recognition, ANSI X3.17-1966.
  3. ^ a b "OCR A". In 1968, American Type Founders produced OCR-A, one of the first optical character recognition typefaces to meet the criteria set by the U.S. Bureau of Standards. The design is simple so that it can be read by a machine, but it is slightly more difficult for the human eye to read. OCR-A follows the 1981 standard set by the American National Standards Institute (ANSI), X-3.17-1981 (size I). The same design is also specified for the German DIN 66008 standard. OCR-B was designed in 1968 by Adrian Frutiger for Monotype. This design pushes the limits of the optical reader, but is easier for people to read. OCR-B's construction follows the ISO 1073/II-1976 (E) standard, with 1979 corrections (letterpress design, size I). Both OCR-A and OCR-B have "alternate" versions, which have the standard ISO-Adobe character set instead of the more limited OCR character set.
  4. ^ Motivation for OCR-A from Microscan
  5. ^ "Background on OCR from Embedded Software Engineering". Archived from the original on 2016-09-17. Retrieved 2012-09-01.
  6. ^ The MetaFont sources for OCR-A from CTAN
  7. ^ John Sauter's 2004 OCR-A font from those MetaFont sources
  8. ^ The fonts-ocr-a Debian packages, based on John Sauter's SourceForge project
  9. ^ Luc Devroye's account of his changes to John Sauter's implementation of OCR-A
  10. ^ Matthew Skala's home page
  11. ^ The mftrace Debian package
  12. ^ Matthew Skala's 2012 OCR-A font from the MetaFont sources
  13. ^ Hoefler, Jonathan. "Two Fools". Hoefler & Co. Retrieved 18 September 2021.
  14. ^ "Technology, Fall '97". Rolling Stone. No. 774. 1997-11-27. p. 59.
  15. ^ "OCR-X typeface". Maxitype. Retrieved 24 September 2023.
  16. ^ "The History of OCR". Data Processing Magazine. 12: 46. 1970.
  17. ^ "Description of a lockbox service, note "The bill contains an invoice and a statement with patient information contained in a scannable Optical Character Recognition (OCR) line. The OCR line is similar in appearance to that found on a credit card statement or telephone bill."" (PDF). Archived from the original (PDF) on 2017-03-01. Retrieved 2015-07-30.
  18. ^ a b c d e ISO/TC97/SC2 (1985-08-01). Japanese OCR-A Graphic Character Set (PDF). ITSCJ/IPSJ. ISO-IR-91.{{citation}}: CS1 maint: numeric names: authors list (link)
  19. ^ BSI (1975-12-01). The set of graphic characters of the United Kingdom 7-bit data code (PDF). ITSCJ/IPSJ. ISO-IR-4.
  20. ^ "Optical Character Recognition" (PDF). Unicode Consortium. Archived (PDF) from the original on 4 January 2023. Retrieved 4 January 2023.
  21. ^ Linotype's OCR-A font: choose Character Map to see the characters and their coding
  22. ^ Linotype's OCR-A Extended font: choose Character Map then Show all
  23. ^ PrecisionID User Guide for the PrecisionID implementation of the OCR-A font
  24. ^ Information page for the Barcode implementation of the OCR-A font
  25. ^ Another source of information about the Barcode fonts
  26. ^ Information page for the Morovia implementation of the OCR-A font
  27. ^ Information page for the IDAutomation implementation of the OCR-A and OCR-B fonts
[edit]
Wikimedia Commons has media related to OCR-A.
Retrieved from "https://wiki.riteme.site/w/index.php?title=OCR-A&oldid=1264654279#Additional_characters"