2D Barcode
PDF417
Linear Barcode
PDF417
PDF417 is a 2D (two-dimensional) symbology which invented by Dr. Ynjiun P. Wang at Symbol Technologies in 1991. PDF417 is acronym for Portable Data File 417. It defines each pattern of barcode is17 units long, and each pattern is composed of 4 bars and spaces. High capacity helps PDF417 gains popularity in many applications like identification system, materials labeling and transportation system. Two-dimensional Barcode PDF417 could be read by a 2-D scanner or a CCD scanner. PDF417 is defined by the international standard ISO/IEC 15438:2006.
Structure of PDF417
Each patten of PDF417 is 17 units long which contain 4 bars (dark) and 4 spaces (light). Each pattern started with a bar and finished with a space. PDF417 is consisted of 3 to 90 linear rows of stacked codewords. Each codeword is divided into three different clusters. The symbol characters is represented in a cluster conform in accordance with the rules of the structures. And each row contains same width and number of codewords. A leading quiet zone: Mandated min amount of white space and surrounds four sides of the barcode PDF417.
  • A start pattern
  • A "row left": Contains information like row number & error correction level
  • 1-30 data codewords: Codewords is consisted of a group of bars and spaces
  • A "row right" to indicate the symbol character
  • A stop pattern
  • A trailing quiet zone
There are forty sizes of QR Code 2005 symbol from version 1 to Version 40. QR Code ranges from 21 X 21 cells to 105 X 105 cells. Each cell encodes one bit and increase by degrees of four cells.
Encoding Data of PDF417
PDF417 is capable of encoding the text, data bytes, numeric digits and pictures. PDF417 has 929 available codewords which consisted of 900 used for data and 29 for special functions.
  • Text Compaction mode: It encodes all printable ASCII characters up to 1,800 characters. The characters are values 32-126 based on ISO/IEC 646. One or two characters are represented by each codeword.
  • Byte Compaction mode: It encodes all 256 possible 8-bit byte values and value 0 to 127 of ASCII characters. Every 6 bytes are represented by a group of 5 codewords.
  • Numeric Compaction mode: 44 decimal digits are represented by a group of 15 codewords.
And the barcode size of the PDF417 should be consisted of: 3 to 90 numbers of rows, 1 to 30 numbers of columns. Width of the modules (including the quiet zones) should be 90X to 583X. Maximum codeword should be 928 while maximum data codeword should be 925 codewords.
Error Correction of PDF417
Like other 2D barcode Data Matrix ECC 200 and QR Code, PDF417 employs a Reed-Solomon (RS) algorithms error correction instead of check digits. By adding "t" check symbols to the data, the Reed-Solomon (RS) algorithms could detect and correct random symbols errors. The error correction has 9 levels which range from 0 to 8. The recommended minimum level is 2. But the data amount, symbol size and encoding capabilities must be considered for an ideal error correction level. The following chart displays the number of error correction codewords and EC level that are recommended by AIM.
  • Correction Level: Total No. of codewords: 2
  • Correction Level: Total No. of codewords: 4
  • Correction Level: Total No. of codewords: 8
  • Correction Level: Total No. of codewords: 18
  • Correction Level: Total No. of codewords: 32
  • Correction Level: Total No. of codewords: 64
  • Correction Level: Total No. of codewords: 128
  • Correction Level: Total No. of codewords: 256
  • Correction Level: Total No. of codewords: 512
At level 0, the maximum number of data be encoded is 925. Including 1 850 characters of Text Compaction mode, 1 108 characters of Byte Compaction mode and 2 710 characters of Numeric Compaction mode.

The maximum number of codewords be encoded is 863 at the minimum recommended error correction level. Including 1 726 characters of Text Compaction mode, 1 033 characters of Byte Compaction mode and 2 528 characters of Numeric Compaction mode.