2D PDF-417 Barcode Symbology Overview
PDF-417 barcode character set, structure & recommended barcode generator for ASP.NET, Winforms, Word and Excel
What is PDF-417
PDF-417, short for Portable Data File 417, is a 2D/matrix barcode symbology which was designed by Dr. Ynjiun P. Wang at Symbol Technologies in 1991. It is stacked, self-checking, bi-directionally decodable barcode symbology which is excellent for encoding large amounts of data. 417 indicates that each pattern of barcode is17 units long, and each pattern is composed of 4 bars and spaces.
PDF-417 is able to encode the text, data bytes, numeric digits and pictures and is widely used in many applications like identification system, materials labeling and transportation system. PDF417 is defined by the international standard ISO/IEC 15438:2006.
PDF-417 Barcode Generator for .NET Applications
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Detailed Information for PDF-417 Barcode Symbology
- Standard ASCII characters
- Extended ASCII characters
PDF-417 Structure
Each pattern of PDF-417 is 17 units long which contain 4 bars (dark) and 4 spaces (light). Each pattern started with a bar and finished with a space. PDF-417 is consisted of 3 to 90 linear rows of stacked codewords. Each codeword is divided into three different clusters.
- A leading quiet zone
- Start character
- Left row indicator symbol character
- 1 to 30 symbol characters
- Right row indicator symbol character
- Stop character
- A trailing quiet zone
Encode Data Mode of PDF-417
- Text Compaction mode allows users to encode all printable ASCII characters to be encoded, i.e. values 32 - 126 inclusive in accordance with ISO/IEC 646 (IRV), as well as selected control characters.
- Byte Compaction mode permits all 256 possible 8-bit byte values to be encoded. This includes all ASCII characters value 0 to 127 inclusive and provides for international character set support. Every 6 bytes are represented by a group of 5 codewords.
- Left row indicator symbol character
- Numeric Compaction mode permits efficient encoding of numeric data strings and 44 decimal digits are represented by a group of 15 codewords.
Error Correction of PDF417
Like barcode Data Matrix ECC 200 and QR Code, PDF417 employs a Reed-Solomon (RS) algorithms error correction instead of check digits. The Reed-Solomon (RS) algorithms could detect and correct random symbols errors by simply adding t check symbols to the data symbol. The error correction has 9 levels which range from 0 to 8 and the codewords ranges from 2 to 512. So symbol size and encoding capabilities must be considered for an ideal error correction level.