Xiaomi's mobile phone suddenly presses the QR code in the picture and can't recognize what's going on.

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1. Two-dimensional code is a more advanced barcode format than one-dimensional code. One-dimensional code can only express information in one direction (generally horizontal direction), while two-dimensional code can store information in both horizontal and vertical directions. One-dimensional code can only be composed of numbers and letters, while two-dimensional code can store information such as Chinese characters, numbers and pictures, so the application field of two-dimensional code is much wider.

2. 2D barcode/QR code can be divided into stacked/row 2D barcode and matrix 2D barcode. Stacked/row-lined two-dimensional bar codes are formed by stacking multiple rows of short-cut one-dimensional bar codes; The matrix two-dimensional bar code is composed of a matrix, and the binary "1" is represented by a dot at the corresponding element position of the matrix, and the binary "" is represented by a space. The arrangement of dots and spaces constitutes a code. The principle of QR code can be derived from? The principle of matrix QR code and the principle of determinant QR code are described.

3. Stacking type, whose coding principle is based on one-dimensional bar code and piled into two or more lines as required. It inherits some characteristics of one-dimensional bar code in coding design, checking principle and reading mode, and the reading equipment is compatible with bar code printing and one-dimensional bar code technology. However, due to the increase of the number of lines, it is necessary to judge the lines, and its decoding algorithm and software are not exactly the same as one-dimensional bar code. Representative two-dimensional bar codes are: Code 16K, Code 49, PDF417, MicroPDF417, etc.