What is a QR code, what is a QR code?

QR codes belong to a type of matrix two-dimensional code.

The characteristics of QR code

One is high-speed reading (QR is taken from the first letter of "Quick Response"), through the camera from shooting to decoding to display content is about three seconds, there is no requirement for the Angle of the camera;

The second is high capacity and high density. Theoretically, the content can store 7089 digits, 4296 letters and digit mixed characters, 2953 8-bit byte data and 1817 Chinese characters after compression processing.

Three is to support error correction processing, according to the standard documentation of QR code, QR code error correction is divided into 4 levels, respectively:

Level L: up to 7% of errors can be corrected.

Level M: up to 15% of errors can be corrected.

Level Q: Up to 25% of errors can be corrected

Level H: up to 30% of errors can be corrected;

Fourth, structure; Seemingly random graphics, in fact, there is a strict definition of the region, the following is a pattern 2, version 1 QR diagram structure (about the QR code "mode", "version" will be described later) :

In the 21 by 21 matrix above, the black and white areas are designated as fixed locations in the QR code specification, called Finder Pattern and Timing pattern. Image finding and location figures are used to help the decoding program determine the coordinates of specific symbols in the figures.

The yellow area is used to store the encoded data content and error correction information code.

The blue area identifies the Level of error correction (i.e., Level L to Level H) and the so-called "Mask pattern". This area is called "Format Information".

Fifth, expand capacity. The Structure Append feature of QR codes enables a QR code to be decomposed into multiple QR codes, and conversely, data from multiple QR codes can be combined into a single QR code.