The QR Code

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Nowadays we can see QR code everywhere. We scan the icon with our phones and get a lot of information immediately. I will talk about the classification about the QR code.

The QR code can be divided into Stacked code and Matrix code. The Stacked code consists of a multi-line stub stacked with one-dimensional bar code. The Matrix code has a matrix composed of the elements in the matrix corresponding position with the " point " represents a binary " 1 ", with " null " means a binary " 0 ".

1. Stacked QR code

Its coding theory is built on the basis of a one-dimensional codes, and it can be stacked in two or more rows as needed. It inherits some features of one-dimensional code in the code design, verification principle, reading methods, and bar code reading device is compatible with the one-dimensional bar code technology. However, due to the increased number of lines, the line needs to be verified, and its decoding algorithm and software is not exactly the same in the one-dimensional bar code. There are some representative line row-dimensional bar codes, like Code 16K, Code 49 and PDF417, etc.

2. Matrix QR code

It is in a rectangular space that is encoded by a black and white pixels in the matrix of different distributions. The corresponding element position in the matrix, with the point, square dots, or other shapes appears to represent a binary “ 1 ”, the point does not appear to represent a binary “ 0 ”, and the permutations and combinations of the point have the meanings. To sum up, Matrix QR code is based on computer image processing technology, such as coding theory. There are some representative matrix bar codes, like Code One, Maxi Code, OR code and Data Matrix, etc.

References:
[1] Quickmark.com, how to make a qr code.
http://www.quickmark.com.tw/Cht/qrcode-datamatrix-generator/default.asp?qrLink
[2] Different kinds of the QR codes.
https://www.unitag.io/qrcode/what-are-the-different-types-of-qrcodes