Glossary

Definitions for the barcode terms used throughout the pyStrich documentation.

1D barcode

A linear symbology that encodes data as parallel bars and spaces of varying widths, read along a single axis. EAN-13, Code 128 and Code 39 are 1D barcodes.

2D barcode

A matrix or stacked symbology that encodes data in two dimensions, giving much higher data density than a 1D barcode. QR Code, Data Matrix, Aztec Code and PDF417 are 2D barcodes.

codeword

A fixed-size unit of encoded data produced after the payload has been mapped from text or bytes into the format’s internal representation. Codewords are what Reed-Solomon error correction operates on, and the total codeword count fixes the symbol’s data capacity.

direct part marking

Engraving, dot-peening, chemical etching or laser marking a barcode directly onto a physical part, in place of a printed label. Used where labels would not be suitable.

DPI

Dots per inch. The resolution at which a printer lays down ink or a scanner samples an image. DPI sets the lower bound on how small a module can be reproduced reliably.

DXF

Drawing Exchange Format. A CAD-oriented vector file format originally from AutoCAD, useful for handing barcode geometry to engraving or laser-cutting workflows.

ECI

Extended Channel Interpretation. A standardised escape mechanism (defined by AIM) that lets a 2D symbol declare which character encoding – UTF-8, ISO-8859-1 and so on – the following data uses, so decoders return text in the right charset.

EPS

Encapsulated PostScript. A vector format for embedding a PostScript drawing inside another document, long-used in print production and still accepted by most prepress and imposition tools.

error correction level

The amount of redundancy a symbol carries, expressed differently per format: QR Code uses L / M / Q / H, PDF417 uses levels 0-8, Aztec Code uses a percentage. Higher levels recover from more damage at the cost of holding less payload.

finder pattern

A distinctive marker at fixed positions inside a 2D symbol so scanners can locate the code and determine its orientation. Each symbology uses its own design: QR Code’s three corner squares, Data Matrix’s solid-L, Aztec Code’s central bullseye.

FNC1

Function Code 1. A non-data control character that 2D symbols use to signal that the payload follows the GS1 Application Identifier format. It is always emitted at the start of the data and may also separate variable-length identifiers within the payload.

GS1

A global standards body that maintains identifiers such as the GTIN and the Application Identifier format used to encode structured product data in barcodes. “GS1 mode” in a 2D symbol uses FNC1 to mark the payload as following these rules.

GTIN

Global Trade Item Number. The GS1 identifier used to uniquely identify a retail product, structured as a 14-digit number with a check digit. EAN-13 barcodes carry GTINs directly; 2D symbols can carry them inside GS1 Application Identifier payloads.

module

The smallest individual element of a barcode: one dark or light unit. In 2D symbologies it is a square cell; in 1D symbologies it is the narrowest bar or space. Symbol sizes and quiet zones are both measured in modules.

occlusion

Partial covering of a symbol by another object – a finger, a sticker, a smudge, a tear. Error-correction codewords let a decoder recover the payload as long as the occluded area stays within tolerance.

projective distortion

The geometric warping that appears when a flat symbol is photographed from an angle: parallel edges no longer stay parallel and modules vary in size across the image. Decoders correct for it using known reference points such as alignment patterns.

quiet zone

The blank margin around a barcode that lets a scanner separate the symbol from surrounding artwork. Most specifications mandate a minimum quiet zone in modules; without it, decoders may fail to lock on or may misread the outer edges.

Reed-Solomon

A widely-used error-correction algorithm that adds redundant codewords to a message so the original data can be recovered even if some codewords are damaged or unreadable. Used by Data Matrix, QR Code, Aztec Code, PDF417 and many other formats.

symbology

A specification defining how data is encoded as a barcode: the character sets it accepts, how codewords are laid out, the error correction it applies, and how a scanner should read it. Data Matrix and QR Code are symbologies.

timing pattern

A row or column of alternating dark and light cells inside a 2D symbol that lets a scanner count modules across the symbol and recover from grid skew. Data Matrix has one along the top and right of each region; QR Code has one row and one column between the corner finders.

X-dimension

The width of the narrowest bar or module in a printed symbol, traditionally measured in mils or millimetres. The X-dimension sets how small the symbol can be printed and how far away a scanner can read it from.