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| Typeface | OCR-A |
|---|---|
| Category | Sans-serif |
| Designer(s) | USA Bureau of Standards |
| Date released | 19681 |
In the early days of computer Optical Character Recognition, there was a need for a font that could be recognized by the slow computers of that day, and by humans2. The resulting compromise was the OCR-A font, which used simple, thick strokes to form recognizable characters. The font is monospaced, with the printer required to place glyphs 0.1 inch apart, and the reader required to accept any spacing between 0.9 and 0.18 inch.
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Standardization
The OCR-A font was standardized by the American National Standards Institute (ANSI) as X3.4-1977. X3.4 has since become the INCITS and the OCR-A standard is now called ISO 1073-1:1976. There is also a German standard for OCR-A called DIN 66008.
All of these standards are copyrighted, and none have been placed on the World Wide Web with the permission of the copyright holders.
Implementations
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 read3.
As metal type gave way to computer-based typesetting, Tor Lillqvist used MetaFont to describe the OCR-A font. That definition was subsequently improved by Richard B. Wales. Their work is available from CTAN 4.
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 5. In 2007, Gürkan Sengün6 created a Debian package from this implementation 7.
In 2008. Luc Devroye corrected the vertical positioning in John Sauter's implementation, and fixed the name of lower case z8.
Apparently unaware of John Sauter's work, Matthew Skala used mftrace 9 and autotrace to convert the Metafont definitions to TrueType format in 2006 10.
In addition to these free implementations of OCR-A, there are also implementations sold by several vendors. 11 12 13 14 15 16 17 18 19.
It is common for implementors of OCR-A to go beyond the standard and define additional glyphs in the same style, to fill unused code points or to meet a particular need20
Use
Although Optical Character Recognition technology has advanced to the point where such simple fonts are no longer necessary, the OCR-A font has remained in use. Some lockbox companies still insist that the account number and amount owed on a blll return form be printed in OCR-A. In addition, some people like it because of its strange look.
Code Points
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.
Space, Digits and Unaccented Letters
All TrueType implementations of OCR-A use U+0020 for space,
U+0030 through U+0039 for the decimal digits,
U+0041 through U+006A for the unaccented upper case letters, and
U+0061 through U+007A for the unaccented lower case letters.
Additional Characters with Obvious Unicode Code Points
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.
| Name | Glyph | Unicode |
|---|---|---|
| Exclamation Mark |  |
U+0021 |
| Quotation Mark |  |
U+0022 |
| Number Sign |  |
U+0023 |
| Dollar Sign |  |
U+0024 |
| Percent Sign |  |
U+0025 |
| Ampersand |  |
U+0026 |
| Apostrophe |  |
U+0027 |
| Left Parenthesis |  |
U+0028 |
| Right Parenthesis |  |
U+0029 |
| Asterisk |  |
U+002A |
| Plus Sign |  |
U+002B |
| Comma |  |
U+002C |
| Hyphen-Minus |  |
U+002D |
| Full Stop (Period) |  |
U+002E |
| Solidus (Slash) |  |
U+002F |
| Colon |  |
U+003A |
| Semicolon |  |
U+003B |
| Less-Than Sign |  |
U+003C |
| Equals Sign |  |
U+003D |
| Greater-Than Sign |  |
U+003E |
| Question Mark |  |
U+003F |
| Commercial At |  |
U+0040 |
| Left Square Bracket |  |
U+005B |
| Reverse Solidus (Backslash) |  |
U+005C |
| Right Square Bracket |  |
U+005D |
| Circumflex Accent |  |
U+005E |
| Low Line |  |
U+005F |
| Grave Accent |  |
U+0060 |
| Left Curly Bracket |  |
U+007B |
| Vertical Line |  |
U+007C |
| Right Curly Bracket |  |
U+007D |
| Tilde |  |
U+007E |
| Pound Sign (Sterling) |  |
U+00A3 |
| Yen Sign |  |
U+00A5 |
| Latin Capital Letter A with Dieresis |  |
U+00C4 |
| Latin Capital Letter A with Ring Above |  |
U+00C5 |
| Latin Capital Letter AE |  |
U+00C6 |
| Latin Capital Letter N with Tilde |  |
U+00D1 |
| Latin Capital Letter O with Stroke |  |
U+00D8 |
| Latin Small Letter O with Dieresis |  |
U+00F6 |
| Latin Small Letter U with Dieresis |  |
U+00FC |
| OCR Hook |  |
U+2440 |
| OCR Chair |  |
U+2441 |
| OCR Fork |  |
U+2442 |
Remaining Characters
The remaining characters of OCR-A, with no obvious Unicode code points, were coded as follows:
| Name | Glyph | Unicode | Unicode Name |
|---|---|---|---|
| Character Erase |  |
U+007F | Delete |
| Long Vertical Mark |  |
U+00A6 | Broken Bar |
| Alternate Hyphen |  |
U+00AD | Soft Hyphen |
| Alternate Apostrophe |  |
U+00B4 | Acute Accent |
| Alternate Period |  |
U+00B7 | Middle Dot |
| Alternate Comma |  |
U+00B8 | Cedilla |
| Alternate Question Mark |  |
U+00BF | Inverted Question Mark |
Exceptions
Some implementations do not use the above code point assignments for some characters.
PrecisionID
The PrecisionID implementation of OCR-A has the following non-standard code points21:
- OCR Hook at U+007E
- OCR Chair at U+00C1
- OCR Fork at U+00C2
- Euro Sign at U+0080
Barcodesoft
The Barcodesoft implementation of OCR-A has the following non-standard code points22:
- OCR Hook at U+0060
- OCR Chair at U+007E
- OCR Fork at U+005F
- OCR Belt Buckle at U+00DD
Moravia
The Moravia implementation of OCR-A has the following non-standard code points23:
- OCR Hook at U+007E
- OCR Chair at U+00F0
- OCR Fork at U+005F
- Vertical Line at U+007C
IDAutomation
The IDAutomation implementation of OCR-A has the following non-standard code points24:
- OCR Hook at U+007E
- OCR Chair at U+00C1
- OCR Fork at U+00C2
- OCR Belt Buckle at U+00C3
In addition, the IDAutomation implementation of OCR-A includes the Euro Sign character. The IDAutomation documentation does not specify the code point for the Euro Sign character. Since the code points for OCR Hook, OCR Chair and OCR Fork match those of PrecisionID, the IDAutomation OCR-A font may be a clone of the PrecisionID OCR-A font, in which case the Euro Sign would be coded as U+0080. The standard code point for Euro Sign is U+20AC.
Sellers of OCR-A font standards
- Hardcopy of ISO 1073-1:1976, distributed through ANSI, from Amazon.com
- ISO 1073-1 is also available from Techstreet, who distributes standards for ANSI and ISO
See also
- MICR
- Optical character recognition
- Westminster (typeface), another typeface designed to be machine-readable.
Notes
- ^ Background information about OCR-A from Linotype
- ^ Motivation for OCR-A from Monotype and Linotype
- ^ Background on OCR-A from Adobe
- ^ The MetaFont sources for OCR-A from CTAN
- ^ John Sauter's 2004 OCR-A font from those MetaFont sources
- ^ Gürkan Sengün's home page in Launchpad
- ^ The ttf-ocr-a Debian package, based on John Sauter's SourceForge project
- ^ Luc Devroye's font page, search for Sauter
- ^ The mftrace Debian package
- ^ Matthew Skala's 2006 OCR-A font from the MetaFont sources
- ^ Bitstream OCR-A font sold by MyFonts
- ^ Linotype OCR-A font sold by Monotype Imaging, Inc.
- ^ Linotype OCR-A font sold by Linotype
- ^ OCR-A font sold by Ascender Corp.
- ^ OCR-A font sold by Azalea Software
- ^ OCR-A and OCR-B fonts sold by Precision ID
- ^ OCR-A and OCR-B fonts sold by Barcodesoft
- ^ OCR-A and OCR-B fonts sold by Moravia Fontware
- ^ OCR-A and OCR-B fonts sold by IDAutomation. Includes a good description and several formats.
- ^ The Unicode code points for Linotype's implementation of OCR-A.
- ^ PrecisionID User Guide for the PrecisionID implementation of the OCR-A font
- ^ Information page for the Barcode implementation of the OCR-A font
- ^ Information page for the Moravia implementation of the OCR-A font
- ^ Information page for the IDAutomation implementation of the OCR-A and OCR-B fonts
External Links
- Information page of linotype.com OCR-A
- Introductory article about OCR fonts
- Link standard ANSI INCITS 17-1981 (R2002)
- Background on ISO work involving OCR-A
- Unicode code charts
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