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Principle of Datamatrix Barcodes
Datamatrix (or Data Matrix) is a high density 2 dimensional barcode that can encode up to 3116 characters from the entire 256 byte ASCII character set. Compared with DF417 barcode symbology the datamatrix barcode belongs to newer family of 2 dimensional barcodes that makes better use of both dimensions and thus can achieve higher data capacity than the PDF417 symbology (~3kB vs ~2kB). The symbol is built on a square grid which have a finder pattern around the edges of the symbol to allow a scanner to identify the barcode. The finder pattern makes it possible to read the barcode regardless of the physical orientation of the code.
In the same way as with other 2 dimensional barcodes the datamatrix code includes error correction capability in order to be resilient towards physical damages of a code. Originally data matrix used an older convolutional error correction schema (ECC) but that has later been changed to use a Reed-Solomon type of error correction which is much more efficient. The older ECC version is known as ECC 000 to ECC 140 and should be considered obsolete and should not be used in new applications.
The newer error correction schema (with Reed-Solomon codes) is known as ECC 200 schema and is the current and recommended schema. By default the library will use the newer schema but support also exists for legacy applications to use the older ECC schema.
The image shows an annotated Datamatrix where the finder and synchronization patterns have been highlighted.
Even though it is primarily designed to handle the the Western alphabet (ISO-8859/x code tables) it will support user prepared Unicode characters through the use of the "Extended Channel Interpretation" (ECI) mechanism. However description of the ECI standard is out of scope for this manual and the interested reader are referred to the official ECI standard document.
Datamatrix standard has been adopted by (among others) "The American National Standards Institute" (ANSI) as a standard symbology and a number of industry standard associations (e.g. EIA, SEMI, AIAG, ATA) where it has been recommended for use.
Summary of features offered in the library
The following list summarizes the features that the library offers for
Datamatrix barcodes. Some of the terms used here assumes familiarity with
Datamatrix barcodes. All terms are also described in the remainder of this
chapter.
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Supports both the new ECC 200 variant and the older ECC 140
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Output formats
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Supports all recommended encodation formats
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ASCII
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C40
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BASE256
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Text
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X12
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Supports all specified symbol sizes
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Supports both auto and user selectable encodation
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Supports both auto and user selectable symbol size
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Supports user specified module size
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Supports custom color specification (foreground, background)
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Supports user specified quiet zone
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Supports easy handling of non-printable characters through the use of special
escape sequences ("Tilde" - processing)
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Supports concatenated symbols
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Symbols can be written directly to a file or sent back as an image to the
browser
Limitation of the JpGraph Datamatrix implementation
This version of the library does not support the EDIFACT compaction standard due to the very specialized and limited use of this encodation schema.
Datamatrix standard
Datamatrix as a standard is fully described in the ISO/IEC 16022E
International Standard and is available for purchase from the
ISO Standard Organization.
Additional information about Data Matrix code is available in the following
United States patents: 4,939,354; 5,053,609; 5,124,536. See
US
patent Office for full disclosures of these patents.