2D Barcode PDF-417 Symbology Introduction

Information about PDF-417 and generate PDF-417 barcode in .NET winforms, asp.net, c# and vb.net
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PDF417 Barcode Symbology Overview
Definition of PDF417
PDF-417, a 2D bar code type, was developed by Symbol Technologies Company in the United States in 1992.
Application of PDF417
  • National defense
  • Public security
  • Transportation
  • Identification cards
  • Industry
  • Commerce
Barcode Specification of PDF417
  • ISO / IEC 15438 (2nd edition 2006-06-01)
PDF417 Barcode Features Overview
  • It is a continuous, multi-row, two-dimensional, and bi-directionally decodable symbology. It has the nature of self-checking and its selectable error correction is 2 to 512 code words per symbol.
  • Encodable characters
    • It can encode all printable ASCII characters and selected control characters for Text Compaction mode.
    • All 256 possible 8 bit-byte values, including all ASCII characters value 0~127 can be encoded for Byte Compaction mode.
    • Numeric Compaction mode allows efficient encoding of numeric data strings.
    • It can encode as many as 811,800 different character sets or data interpretations.
    • Different function codewords for control purposes.
  • Symbol capacities
    • The largest codeword capacity is 928 code words.
    • The maximum data codeword capacity is 925 code words, and it can encode 1,850 characters for Text Compaction mode, 1,108 characters for Byte Compaction mode and 2,710 characters for Numeric Compaction mode.
    • There is a maximum of 863 data codewords at the minimum recommended error correction level and it can encode 1,726 characters for Text Compaction mode, 1,033 characters for Byte Compaction mode and 2,528 characters for Numeric Compaction mode.
  • Symbol size
    • It has 3 to 90 rows and 1 to 30 columns.
    • Width of the symbol is 90X to 583X including quiet zones.
    • Non-data overhead per row are 73 modules, including quiet zones.
    • The minimum width of a module (X) depends on the application, and it shall be fixed throughout a given symbol.
    • The row height should be at least 3X.
    • The minimum size of the quiet zones is equal to 2X.
  • Per symbol character, which is 17 modules in width, contains 8 elements, including 4 bars and 4 spaces, and the largest element is 6 modules wide.
  • There are some inherent or optional additional features:
    • Data compaction (inherent)
    • Extended Channel Interpretations (optional, Refer to number 5)
    • Macro PDF417 (optional)
    • Edge to edge decodable (inherent)
    • Cross row scanning (inherent)
    • Compact PDF417 (optional)
PDF417 Barcode Structure Overview
Each PDF417 row, from left to right, includes: Leading Quiet Zone, Start Pattern, Left Row Indicator Codewords, Data Codewords, Right Row Indicator Codewords, Stop Pattern, and Trailing Quiet Zone
Extended Channel Interpretations (ECI)
ECI, identified by a 6-digit number, enables PDF 417 encode multiple character sets (e.g. Arabic, Greek, Italian) and other data interpretations into one PDF417 symbol.
PDF417 is only a data carrier, while ECI scanner can transmit the information from one language to another. There are 5 types of interpretations for PDF-417:
  • Character sets, aliased code pages
  • General purpose interpretations
  • User defined interpretations for closed system
  • Transmission of control information for Macro PDF417
  • Transmission of uninterpreted PDF-417 code words
Compact PDF417
Compact PDF417, completely compatible to the standard PDF417, is used when space considerations are a primary concern and there is no symbol damage. In this circumstance, the right row indicators may be omitted and the stop pattern may be reduced to one module width bar.
A Compact PDF417 symbol with fewer than 6 rows is not error corrected, and therefore it’s very easy to be damaged or be printed with low quality.