IEC INTERNATIONAL 15415 STANDARD.pdf

The benefit of calibration is that when an image is captured of any other code, if that code is darker, it will appear darker when captured using that exposure time. Essentially it establishes a baseline for the verification software reflectance values. Currently, there are no DPM-specific calibration cards to challenge ISO 29158. A Data Matrix conformance test card can be used, but the contrast values will never perfectly match the value on the card because of the image adjustment used in 29158. Testing with the 29158 grading standard can be done to check for correct operation but will yield results that are different than those shown on the conformance card. It is recommended that the verifier also be tested using ISO 15415.

The aperture, global threshold, lighting options, image sensor, and calibration all differ between the ISO 15416 and ISO/IEC TR 29158 grading standards. To learn more about the grading process and quality parameters of ISO standards, download the Understanding Verification Results Whitepaper.

ISO/IEC 15415:2011 applies to those two-dimensional symbologies for which a reference decode algorithm has been defined, but its methodologies can be applied partially or wholly to other similar symbologies.

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While ISO/IEC 15415:2011 can be applied to direct part marks, it is possible that better correlation between measurement results and scanning performance will be obtained with ISO/IEC TR 29158 in combination with ISO/IEC 15415:2011.

Labels of grades for all tuple elements returnedwhen calling get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResults with'quality_isoiec15415'"quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415". The labels are differentdepending on the type of the evaluated data code symbol.

The ECI protocol (Extended Channel Interpretation)is used to change the default interpretation of the encoded data.A 6-digit code number after the ECI character switches theinterpretation of the following characters from the defaultto a specific code page like an international character set.In the output stream the ECI switch is coded as'\nnnnnn'"\nnnnnn""\nnnnnn""\nnnnnn""\nnnnnn""\nnnnnn".Therefore all backslashes('\'"\""\""\""\""\", ASCII code 92), thatoccur in the normal output stream have to be doubled.

Tuple with the assessment of print quality in compliance withthe international standard ISO/IEC 15415. The first elementalways contains the overall print quality of the symbol; thelength of the tuple and the denotation of the remainingelements depend on the specific data code type. According tothe standard, the grades are whole numbers from 0 to 4, where0 is the lowest and 4 the highest grade. It is important tonote what, even though the implementation is strictly basedon the standard, the computation of the print quality gradesdepends on the preceding decoding algorithm. Thus, differentdata code readers (of different vendors) can potentiallyproduce slightly different results in the print qualityassessment.

We recommend to use high quality images without artefactslike defocus, noise, overexposure, or inhomogeneousillumination. Such artefacts influence the result of theprint quality grading. Further, to obtain robust gradingresults, an effective resolution of at least ten pixels permodule in width and height is required (see ISO/IEC 15415,Chapter 7.3.3).The quality grades are only computed when the symbol region including the quietzone is fully in the image, elsewise -1 is returned for the quality grades.

The definition of the respective elements is as follows: Theoverall quality is the minimum of all individual grades.The contrast is the range between the minimal and themaximal pixel intensity in the data code domain, and a strongcontrast results in a good grading. The modulationindicates how strong the amplitudes of the data code modules are.Big amplitudes make the assignment of the modules to black orwhite more certain, resulting in a high modulation grade. It is tonote that the computation of the modulation grade is influenced bythe specific level of error correction capacity, meaning that themodulation degrades less for codes with higher error correctioncapacity. The contrast uniformity is the minimum modulation value foundin any module. This value is no grade, therefore, it can have real values. It does not affect the overall quality. According to ISO/IEC15415, the print growth is no grade andis therefore not used for calculating the overall quality.Instead, it can be used as an additional information to find out,if the graphical features comprising the symbol have notshrunk or grown from their nominal size. This means that theprint growth gives some indication to which extent the darkand light modules fill out their module boundaries.The calculation of the print growth does not follow the scheme asspecified by ISO/IEC 15415, but instead it considers thespecifications as stated by the ISO/IEC standard of the 2D data codeto be examined. This means that the computation of theprint growth for Aztec Codes is implemented asdescribed in ISO/IEC 24778:2008. For ECC 200 thecorresponding standard is ANSI/AIM International Specification DataMatrix and for QR Codes as well as forMicro QR Codes the implementation follows ISO/IEC 18004:2006.For all 2D data codes described above, the print growth iscalculated in horizontal and vertical direction. The reported grade isthe lower rated of the pair.

The aperture is the size of the synthesized aperturein units of the module size of the symbol. This aperture isused to obtain the reference gray scale image during thegrading procedure. It is defined in ISO/IEC 15415, Chapter7.3.3.

returns a tuple with the raw values for all 'directly measurable' grades (reported by 'quality_isoiec15415'"quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415").These are grades, whose definition in the ISO/IEC 15415 standardis a 'direct derivative' of the reflectance (i.e., thegray values) or of geometrical properties of the symbol, or gradesthat are the result of a 'direct counting'.

The returned tuple has the same order of elements as thecorresponding result with 'quality_isoiec15415'"quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415""quality_isoiec15415". For thegrades, which are excluded from these lists, the operator reports'N/A'"N/A""N/A""N/A""N/A""N/A". For the 2D data codes ECC 200,Aztec Code, QR Code, and Micro QR Code theexcluded grades areoverall quality, modulation,fixed pattern damage, decode andreflectance margin.For the 2D stacked code PDF417 the excluded grades areoverall quality, start/stop pattern,modulation, decodability, defects.

Tuple with intermediate results that are determined duringthe assessment of print quality for ECC 200 codes incompliance with the international standard ISO/IEC 15415:2011and ISO/IEC 16022:2006. Using these values requires athorough understanding of the underlying algorithms, and westrongly recommend to read ISO/IEC 15415:2011 and ISO/IEC16022:2006 along with this documentation.

A description of the intermediate results is given below. Thereturned intermediate grades ('quality_isoiec15415_intermediate'"quality_isoiec15415_intermediate""quality_isoiec15415_intermediate""quality_isoiec15415_intermediate""quality_isoiec15415_intermediate""quality_isoiec15415_intermediate") and values ('quality_isoiec15415_intermediate_values'"quality_isoiec15415_intermediate_values""quality_isoiec15415_intermediate_values""quality_isoiec15415_intermediate_values""quality_isoiec15415_intermediate_values""quality_isoiec15415_intermediate_values") are the minimalgrades and values for the code under inspection. The names of theavailable intermediate results can be queried with 'quality_isoiec15415_intermediate_labels'"quality_isoiec15415_intermediate_labels""quality_isoiec15415_intermediate_labels""quality_isoiec15415_intermediate_labels""quality_isoiec15415_intermediate_labels""quality_isoiec15415_intermediate_labels".

Tuple with the reflectance margin module grades that are determinedduring the assessment of print quality according to the ISO/IEC 15415standard Chapter 7.8.4.3. This includes the finder pattern modulesand the 4 quiet zones adjacent to the symbol (2 horizontal and2 vertical).

Tuple with the image row coordinates of the points within the symbolmodules for which the module grades are computed with the parameter'quality_isoiec15415_reflectance_margin_module_grades'"quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades".

The returned tuple has the same number and order of elements as thecorresponding result with'quality_isoiec15415_reflectance_margin_module_grades'"quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades".

Tuple with the image column coordinates of the points within thesymbol modules for which the module grades are computed with theparameter'quality_isoiec15415_reflectance_margin_module_grades'"quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades""quality_isoiec15415_reflectance_margin_module_grades".

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