Android Code 128 条码的最大长度
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Maximum length of a Code 128 barcode
提问by Divya
I need to create a Code 128 barcode with a maximum of 44 characters. What is the maximum number of characters supported by the Code 128 barcode format?
我需要创建一个最多 44 个字符的 Code 128 条码。Code 128 条码格式支持的最大字符数是多少？
I came to know that Code 128 can encode all 128 characters of ASCII, but I cannot determine the maximum number of characters it supports.
我开始知道 Code 128 可以编码 ASCII 的所有 128 个字符，但我无法确定它支持的最大字符数。
回答by Terry Burton
The specification for Code 128 (ISO/IEC 15417) leaves the maximum length undefined and states that this is something that should be defined by any derivative application[*]standard:
Code 128 (ISO/IEC 15417) 规范未定义最大长度，并指出这是任何衍生应用程序[*]标准都应定义的内容：
4.7.1 Symbology and data characteristics
Application specifications should consider the following parameters.
b) The number of data characters in the symbol, which may be fixed, variable or variable up to a defined maximum.
4.7.1 符号和数据特征
应用规范应考虑以下参数。
b) 符号中的数据字符数，它可以是固定的、可变的或可变的，直到定义的最大值。
For example the GS1 General Specification define that GS1-128 (the formal application of Code 128 to the supply chain industry) has a limits of 48 characters per symbol:
例如，GS1 通用规范定义 GS1-128（Code 128 在供应链行业的正式应用）每个符号的限制为 48 个字符：
5.4.1 GS1-128 Bar Code Symbol size characteristics:
The characteristics of the GS1-128 Symbology are:
GS1-128 Bar Code Symbol size characteristics:
- The maximum number of data characters in a single symbol is 48.
5.4.1 GS1-128 条码符号尺寸特性：
GS1-128 符号体系的特点是：
GS1-128条码符号尺寸特性：
- 单个符号中的最大数据字符数为 48。
Practically one should restrict the number of characters to whatever fits comfortably in a scanner's field of view. This will vary depending on the type and model of the device, e.g. handheld vs fixed, laser vs CCD, high-end vs budget, etc. In uncontrolled or open environments a high degree of tolerance should be budgeted for.
实际上，应该将字符数限制为适合扫描仪视野的任何字符数。这将根据设备的类型和型号而有所不同，例如手持与固定、激光与 CCD、高端与预算等。在不受控制或开放的环境中，应为高度的容忍度做预算。
It is especially worth noting that Code 128 supports double-density compression of numeric data ("mode C") which makes encoding long strings of digits much more efficient.
尤其值得注意的是，Code 128 支持数字数据的双密度压缩（“模式 C”），这使得对长数字字符串的编码效率更高。
Here is a 44-digit Code 128 containing 12345678901234567890123456789012345678901234:
这是一个 44 位代码 128，其中包含12345678901234567890123456789012345678901234：
This is appropriately sized for most practical applications.
对于大多数实际应用，这是适当的大小。
However, here is the same Code 128 this time containing 44 alpha characters ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCD:
但是，这次是相同的 Code 128，包含 44 个字母字符ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCD：
A barcode of this size will not be useful in as many applications since reading this reliably would require a scanner with a high resolution and wide field-of-view.
这种尺寸的条码在许多应用中都没有用处，因为要可靠地读取它需要具有高分辨率和宽视野的扫描仪。
So ultimately the maximum length of a Code 128 is dependant not only on the practical constraints of the application but also the type of data to be encoded.
因此，最终 Code 128 的最大长度不仅取决于应用程序的实际约束，还取决于要编码的数据类型。
[*] Application is the industry term referring to the environment and processes in which the barcode system is to be used, rather than any specific software application.
[*] 应用程序是行业术语，指的是使用条码系统的环境和过程，而不是任何特定的软件应用程序。
