BS ISO IEC 30116 pdf download.Information technology — Automatic identification and data capture techniques — Optical Character Recognition (OCR) quality testing
1 Scope
This document — specifies the methodology for the measurement of specific attributes of OCR-B character strings, — defines a method for evaluating these measurements and deriving an overall assessment of character string quality, — defines a reference decode algorithm for OCR-B, and — gives information on possible causes of deviation from optimum grades to assist users in taking appropriate corrective action. This document applies to OCR-B as defined in ISO 1073-2, but its methodology can be applied partially or wholly to other OCR fonts.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia.org/ — ISO Online browsing platform: available at http://www.iso.org/obp 3.1 binarized image binary (black/white) image created by applying the global threshold to the pixel (3.5) values in the reference grey-scale image 3.2 document reference edge physical (i.e. mechanical) end of the surface with the MRZ whose position is determined by putting a black background under the surface with the MRZ and sliding the document up against a physical stop 3.3 inspection area rectangular area which contains the entire symbol (3.11) to be tested inclusive of its quiet zones 3.4 character outline limits outlines of an ideal printed image of a character Note 1 to entry: This is a qualitative evaluation utilized in ISO 1831 that is replaced in this document with SWT.3.5 pixel individual light-sensitive element in a light-sensitive array Note 1 to entry: Examples of light-sensitive array are CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) device. 3.6 raw image matrix of the reflectance values in x and y coordinates across a two-dimensional image, derived from the discrete reflectance values of each pixel (3.5) of the light-sensitive array 3.7 reference grey-scale image raw image (3.6) convolved with a synthesized circular aperture 3.8 scan grade result of the assessment of a single scan of an OCR symbol, derived by taking the lowest grade achieved for any measured parameter of the reference grey-scale and binarized images (3.1) 3.9 stroke width nominal dimension perpendicular to the direction of the line making up an OCR character 3.10 stroke width template inner and outer character boundaries defined by circles whose centres follow the line created by the character centreline coordinates defined in Annex A 3.11 symbol group of OCR characters comprising the entire machine-readable entity (e.g. Machine Readable Zone (MRZ) as specified in ICAO 9303, sizes ID-1, ID-2 and ID-3) including quiet zones and the document reference edge (3.2) Note 1 to entry: Document sizes are defined in ISO/IEC 7501 (all parts) (ICAO 9303) as TD1, TD2 and TD2, whereas the same sizes are defined in ISO/IEC 7810 as ID-1, ID-1 and ID-3. In this document, we use the terms ID-1, ID-2 and ID-3. 3.12 X-tolerance 0,08 mm for Size I with a nominal stroke width (3.9) of 0,35 mm Note 1 to entry: 0,08 mm for Size I with a nominal stroke width of 0,35 mm was originally defined in ISO 1831:1980, Table 2. 3.13 Y-tolerance 0,15 mm for Size I with a nominal stroke width (3.9) of 0,35 mm Note 1 to entry: 0,15 mm for Size I with a nominal stroke width of 0,35 mm was originally defined in ISO 1831:1980, Table 2.
6 Measurement methodology for OCR-B
6.1 Overview of methodology The basis of the measurement methodology is the evaluation of reflectance from the symbol. This methodology is also intended to correlate with conditions encountered in OCR scanning systems. The method starts by obtaining the raw image, which is a high-resolution grey-scale image of the symbol captured under controlled illumination and viewing conditions. 6.2 Obtaining the test image 6.2.1 Measurement conditions A test image of the symbol shall be obtained in a configuration that mimics the typical scanning situation for that symbol, but with substantially higher resolution (see 6.3.3), uniform illumination and at best focus. The reference optical arrangement is defined in 6.3.4. Alternative optical arrangements may be used provided that the measurements obtained with them can be correlated with the use of the reference optical arrangement. Ambient light levels shall be controlled in order not to influence the measurement results. Whenever possible, measurements shall be made on the symbol in its final configuration, i.e. the configuration in which it is intended to be scanned. For MRTD evaluation, optically personalized samples shall be used. This includes that all layers available at a document including laminations, security features and protective layers shall be present. Two principles govern the design of the optical set-up. First, the test image’s grey-scale shall be nominally linear and not be enhanced in any way. Second, the image resolution shall be adequate to produce consistent readings, which generally requires that the character stroke-widths span at least 10 image pixels.
BS ISO IEC 30116 pdf download
