PDF417-rb implements a PDF417 encoder based on freely available PDF417 specification documentation, and therefore may not be fully compliant with ISO 15438.
- Codeword - A codeword is the encoding unit used to represent the contents of a PDF417 symbol. There are 929 codeword values, 0 to 928, for data encoding. Each numeric codeword value corresponds to bar-space patterns in three sets, or "clusters", of bar-space patterns. Which cluster is used to lookup a codeword is based on the row index of the codeword. Bar-space patterns have four bars and four spaces, and can be divided into seventeen "modules" with each module representing one unit of a bar or space. Bars and spaces can be one to six modules wide, but the total width will always be seventeen modules per codeword.
- High-level encoding - process of converting data into numeric codewords (0 - 928). Three encoding modes exist: Text, Numeric, and Binary.
- Low-level encoding - process of converting numeric codewords into corresponding bar-space representation.