In order to convert input data into a QR code symbol, we’ll go through some step
Data Analysis
A QR code encodes a string of text. The QR standard has four modes for encoding text: numeric, alphanumeric, byte, and Kanji. Each mode encodes the text as a string of bits (1s and 0s), but each mode uses a different method for converting the text into bits, and each encoding method is optimized to encode the data with the shortest possible string of bits.
Therefore, first step should be to perform data analysis to determine whether text can be encoded in numeric, alphanumeric, byte, or Kanji mode, and then select the most optimal mode for your text.
Data Encoding
Next step is to encode text. The result of this step is a string of bits that is split up into data codewords that are each 8 bits long.
The mode used for encoding is identified by the Mode Indicator, which is a string of 4 bits. Encoded data must start with the appropriate mode indicator which is used for encoding.
The number of characters that are being encoded is represented by the string of bits known as Character Count Indicator. Character Count Indicator is placed after the mode indicator and its length is version dependent.
Error Correction Coding
QR codes use error correction. This means that the string of data bits that represent our text, we must then use those bits to generate error correction codewords using a process called Reed-Solomon error correction.
QR scanners read both the data codewords and the error correction codewords. By comparing the two, the scanner can determine that it reads the data correctly or not, and if it did not read the data correctly it can correct errors.
Structure Final Message
The data and error correction codewords generated in the previous steps must now be arranged in the proper order. For large QR codes, the data and error correction codewords are generated in blocks, and these blocks must be interleaved according to the QR code specification.
Module Placement in Matrix
After generating the data codewords and error correction codewords and arranging them in the correct order, you must place the bits in the QR code matrix. The codewords are arranged in the matrix in a specific way.
Data Masking
Certain patterns in the QR code matrix can make it difficult for QR code scanners to correctly read the code. To counteract this, the QR code specification defines eight mask patterns, each of which alters the QR code according to a particular pattern.
Format and Version Information
The last step is to add format and (if necessary) version information to the QR code by adding pixels in particular areas of the code that were left blank in previous steps. The format pixels identify the error correction level and mask pattern being used in this QR code. The version pixels encode the size of QR matrix and are only used in larger QR codes.
