二维码编码技术详解 - ISO/IEC18004标准

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"二维码编码方式是信息技术领域中自动识别和数据捕获技术的一种，具体指QR Code（Quick Response Code）条码编码方式。该标准由ISO/IEC制定，详细规范在ISO/IEC 18004:2000(E)中，首次发布于2000年6月15日。QR Code作为一种二维条码，能够存储比传统一维条码更多的信息，并且可以被快速读取。" QR Code编码方式的详细介绍如下： 1. **结构组成**：QR Code由模块组成，每个模块可以是黑色或白色，构成一个矩阵。它由定位图案、分隔符、校正码、版本信息和数据区域等部分组成。 2. **数据编码**：QR Code能编码各种类型的数据，包括数字、字母、全角字符、二进制数据以及URL、电子邮件地址等。它使用了多个编码模式来适应不同类型的输入数据，如数字模式、字母模式、8位字节模式和KANJI模式。 3. **纠错能力**：为了增强二维码的可靠性，QR Code采用了错误纠正编码，即ECC（Error Correction Coding），分为L、M、Q、H四个等级，可纠正3%到30%的错误。即使二维码部分受损，仍能恢复大部分信息。 4. **版本与容量**：QR Code有40个版本（Version 1至Version 40），版本越高，能存储的信息越多。最小的Version 1可存储42个数字字符，最大的Version 40能存储2953个数字字符。 5. **解码过程**：扫描设备通过识别定位图案找到二维码的四个角落，然后读取数据模块并进行错误校验，将二进制数据转换为可读文本。 6. **应用广泛**：QR Code在商业、广告、物流、移动支付、物联网等领域有着广泛应用。例如，产品包装上的二维码可以链接到产品信息，名片上的二维码可以快速交换联系信息，而付款码则用于无接触支付。 7. **标准兼容性**：ISO/IEC 18004标准确保了不同制造商生产的扫描设备和生成的二维码之间的互操作性，保证了全球范围内的通用性。 8. **安全性考虑**：尽管QR Code提供了高效的数据传输方式，但也有安全风险。用户在扫描二维码时应谨慎，避免点击不明链接，防止个人信息泄露或恶意软件感染。 9. **发展趋势**：随着技术的进步，QR Code也在不断进化，如隐形二维码、动态二维码等新型形式，以满足更多场景的需求。总结来说，二维码编码方式，尤其是QR Code，已经成为现代信息化社会中不可或缺的数据交换工具，其高效、可靠和灵活的特性使得它在众多领域中得以广泛应用。了解并掌握QR Code的相关知识，对于理解和利用这种技术至关重要。

ISO/IEC 18004:2000(E)

Version 14

73 modules

modules

Figure 6 — Version 14 symbol

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ISO/IEC 18004:2000(E)

7.3.2 Finder pattern

The finder pattern shall consist of three identical Position Detection Patterns located at the upper left, upper right

and lower left corners of the symbol respectively as illustrated in Figure 2. Each Position Detection Pattern may be

viewed as three superimposed concentric squares and is constructed of dark 7 ´ 7 modules, light 5 ´ 5 modules

and dark 3 ´ 3 modules. The ratio of module widths in each Position Detection Pattern is 1:1:3:1:1 as illustrated in

Figure 9. The symbol is preferentially encoded so that similar patterns have a low probability of being encountered

elsewhere in the symbol, enabling rapid identification of a possible QR Code symbol in the field of view.

Identification of the three Position Detection Patterns comprising the finder pattern then unambiguously defines the

location and orientation of the symbol in the field of view.

A: 3 modules

B: 5 modules

C: 7 modules

1:1: 3 :1:1

A B C

Figure 9 — Structure of Position Detection Pattern

7.3.3 Separators

A one-module wide Separator is placed between each Position Detection Pattern and Encoding Region, as

illustrated in Figure 2, and is constructed of all light modules.

7.3.4 Timing Pattern

The horizontal and vertical Timing Patterns respectively consist of a one module wide row or column of alternating

dark and light modules, commencing and ending with a dark module. The horizontal Timing Pattern runs across

row 6 of the symbol between the separators for the upper Position Detection Patterns; the vertical Timing Pattern

similarly runs down column 6 of the symbol between the separators for the left-hand Position Detection Patterns.

They enable the symbol density and version to be determined and provide datum positions for determining module

coordinates.

7.3.5 Alignment Patterns

Each Alignment Pattern may be viewed as three superimposed concentric squares and is constructed of dark 5 ´ 5

modules, light 3 ´ 3 modules and a single central dark module. The number of Alignment Patterns depends on the

symbol version and they shall be placed in all Model 2 symbols of Version 2 or larger in positions defined in Annex

7.3.6 Encoding region

This region shall contain the symbol characters representing data, those representing error correction codewords,

the Version Information and Format Information. Refer to 8.7.1 for details of the symbol characters. Refer to 8.9

for details of the Format Information. Refer to 8.10 for details of the Version Information

7.3.7 Quiet zone

This is a region 4X wide which shall be free of all other markings, surrounding the symbol on all four sides. Its

nominal reflectance value shall be equal to that of the light modules.

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Single user licence only, copying and networking prohibited

ISO/IEC 18004:2000(E)

8 Requirements

8.1 Encode procedure overview

This section provides an overview of the steps required to convert input data to a QR Code symbol.

Step 1 Data analysis

Analyze the input data stream to identify the variety of different characters to be encoded. QR Code supports the

Extended Channel Interpretation feature, enabling data differing from the default character set to be encoded. QR

Code includes several modes (see 8.3) to allow different sub-sets of characters to be converted into symbol

characters in efficient ways. Switch between modes as necessary in order to achieve the most efficient conversion

of data into a binary string. Select the required Error Detection and Correction Level. If the user has not specified

the symbol version to be used, select the smallest version that will accommodate the data. A complete list of

symbol versions and capacities is shown in Table 1.

Step 2 Data encodation

Convert the data characters into a bit stream in accordance with the rules for the mode in force, as defined in 8.4.1

to 8.4.5, inserting Mode Indicators as necessary to change modes at the beginning of each new mode segment,

and a Terminator at the end of the data sequence. Split the resulting bit stream into 8-bit codewords. Add Pad

Characters as necessary to fill the number of data codewords required for the version.

Step 3 Error correction coding

Divide the codeword sequence into the required number of blocks (as defined in Tables 13 to 22) to enable the

error correction algorithms to be processed. Generate the error correction codewords for each block, appending

the error correction codewords to the end of the data codeword sequence.

Step 4 Structure final message

Interleave the data and error correction codewords from each block as described in 8.6 (step 3) and add remainder

bits as necessary.

Step 5 Module placement in matrix

Place the codeword modules in the matrix together with the Finder Pattern, Separators, Timing Pattern, and

Alignment Patterns.

Step 6 Masking

Apply the masking patterns in turn to the encoding region of the symbol. Evaluate the results and select the

pattern which optimizes the dark/light module balance and minimizes the occurrence of undesirable patterns.

Step 7 Format and Version Information

Generate the Format and (where applicable) Version Information and complete the symbol.

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