QR Article 1: "Basic QR Characteristics"

This article starts the cycle “QR Code Structure ”. Approximately there will be about 10 articles devoted to the principles of image formation using this code and 2 to 3 articles are devoted to the .Net library, which encodes and decodes this code. The purpose of the cycle is to parse the QR code “by bone” "To help those interested in its rapid development.

Article 1: “Basic QR Characteristics ”

QR Code, like any other representative of two-dimensional bar codes, uses matrix symbolism to operate with the following inherent characteristics:

• Format:
  
  • QR Code , has a full range of features and the maximum supported amount of encrypted information;
  • MicroQR Code , has a shortened header and cut off the amount of encrypted information;
  
  
• Encoding type:
  
  • numeric data (numeric, supports numbers 0-9);
  • alphanumeric data (alpha numeric, supports numbers 0-9, upper case letters AZ, 9 special characters: space, $% * + - / :);
  • byte data (bit by default ISO / IEC 8859-1 );
  • Kanji data ( Kanji packaged in 13 bits);
  
  
• Modular dimensions:
  
  • QR Code , can be from 21x21 modules to 177x177 modules, depending on the Version1 ... Version40 version used, in general, the number of modules increases by 4 with each step;
  • MicroQR Code , can be from 11x11 modules to 17x17 modules;
  
  
• Number of characters per character
  
  • QR Code
    
    • numeric data , numeric 7089 characters;
    • alphanumeric data , alpha numeric 4296 characters;
    • byte data , bit 2953 characters;
    • Kanji data , Kanji 1817 characters;
  • MicroQR Code
    
    • numeric data , numeric 35 characters;
    • alphanumeric data , alpha numeric 21 characters;
    • byte data , bit 15 characters;
    • Kanji data , Kanji 9 characters;
    
    
  
  
• Error Correction Levels (optional)
  
  • L 7%
  • M 15%
  • Q 25%
  • H 30%
  
  In this code, the Reed-Solomon code , which has unique abilities, is used for detection and correction, despite the rather interesting applications of this type of bar code, its main task was to apply to any surface, and the image can be overwritten during operation, and so thanks to the code Reed-Solomon can work wonders of restoration. Who is interested in the article by Chris Kaspersky "The power of Reed-Solomon codes or information that has risen from the ashes."
  

No less interesting are the additional features:

• Structured append - Structured addition (concatenation), provides the ability to combine logically split information into 16 characters, in any sequence without prejudice to recovery.
• Extended Channel Interpretations - Additional interpretation channel, allows you to use a different character set from the default set (for example: Arabic characters, Cyrillic , Greek characters) and other specific sets used in industry standards.
• Reflectance reversal - Reverse reflection, according to the international standard, it is recommended to use black images on a white background, however the possibility of applying white symbols on a black background is supported, it is imperative that this kind of code should be based on the standard one (the easiest way to do this is to swap colors, where black was white and vice versa).
• Mirror imaging - Mirror imaging , according to the standard, detection layers should be located in the upper right, upper left, lower left corners of the image, however, it is possible to use these layers in order of upper left, upper right, lower right, respectively, the positions of the rows and columns of modules are exchanged.

Further 2 drawings describing the last 2 points:


Behind this, I am completing my introductory article, next time I promise to tell you about the purpose of the modules and zones used in the formation of this code.

Sources:
Information technology - Bar code symbology - QR code
Information technology - QR Code 2005 bar code symbology specification
Information technology - Bar code print quality test specification - Two-dimensional symbols