Introduction to the structure of PDF417 bar code system

flutter + Applet + Back end ,3 Individuals can open your APP The way | Registration will be sent to Dajiang Yuntai 、 Huawei watch ！>>>

PDF417 It's in English Portable  data File  Acronyms for three words , Meaning for “ Portable data files ”. Because every symbol character that makes up a bar code has 4 A bar and 4 Empty form , If the narrowest bar or space that makes up the barcode is called a module , Then 4 A bar and 4 The total number of empty modules must be 17, So called 417 Code or PDF417 code .

  Symbolic structure

every last PDF417 Symbols consist of a sequence of layers surrounded by white space .

Each layer includes ： Left margin 、 Start character ; Left indicator character ;1 To 30 Data symbol characters ; Right layer indicator character ; Terminator ; Right margin , Here's the picture ：

 PDF417 Symbolic structure

The structure of symbolic characters

Each symbol character includes 4 A bar and 4 Empty , Every bar or void is caused by 1-6 Modules . In a symbolic character ,4 A bar and 4 The total number of empty modules is 17, Here's the picture ：

 PDF417 The ability to correct mistakes

PDF417 An important feature of two-dimensional bar code is its high ability to correct errors automatically ,  however PDF417 The error correction ability is related to the amount of data that can be stored in each barcode ,PDF417 Code divides error recovery into 9 Level , Its value is from 0 To 8, The higher the level , The better the ability to correct mistakes , But the less data you can store , It is generally recommended that at least 10% Check the word code of . As shown in the figure ：

  That's all about PDF417 Introduction of bar code system , Want to know more about barcode content , Sure Bar code generation software Find the corresponding content .