交叉25码(ITF)编码方式

1、INTERLEAVED 2 OF 5 SYMBOLOGY(ITF)INTERLEAVED 2 OF 5 BACKGROUND INFORMATIONInterleaved 2 of 5 is a higher-density numeric symbology based upon the Standard 2 of 5 symbology. It is used primarily in the distribution and warehouse industry. Interleaved 2 of 5 encodes any even number of numeric characte

2、rs in the widths (either narrow or wide) of the bars and spaces of the barcode. Unlike Standard 2 of 5, which only encodes information in the width of the bars, Interleaved 2 of 5 encodes data in the width of both the bars and spaces. This allows Interleaved 2 of 5 to achieve a somewhat higher densi

3、ty. The symbology is called interleaved because the first numeric data is encoded in the first 5 bars while the second numeric data is encoded in the first 5 spaces that separate the first 5 bars. Thus the first 5 bars and spaces actually encode two characters. This is also why the barcode can only

4、encode an even number of data elements. A typical Interleaved 2 of 5 barcode is: Note that the above barcode is physically smaller than its equivalent representation using Standard 2 of 5. NOTE: Interleaved 2 of 5 is essentially identical to Standard 2 of 5 except for the fact that Interleaved 2 of

5、5 encodes information in both the bars and spaces while Standard 2 of 5 only encodes information in the bars. However, the encoding scheme is the same for both in terms of their use of wide and narrow elements for each element. COMPUTING THE CHECKSUM DIGITInterleaved 2 of 5 is similar to Standard 2

6、of 5 in the sense that it may include an optional modulo 10 check digit. Please see the section concerning Computing the Checksum digit in the Standard 2 of 5 page. The process for calculating the check digit is the same in Interleaved 2 of 5 as it is in Standard 2 of 5. And, like Standard 2 of 5, t

7、he checksum digit is optional. NOTE: In the case of Interleaved 2 of 5, the total length of the value to be encoded must be even. If you are going to compute and append a checksum value, the actual data itself must be odd in length such that when the additional checksum value is appended, the total

8、length will be even. ENCODING THE SYMBOLIn the following text, we will discuss the encoding of the barcode by considering that the number 1 represents a dark or bar section of the barcode whereas a 0 represents a light or space section of the barcode. Thus the numbers 1101 represents a double-wide b

9、ar (11), followed by a single-wide space (0), followed by a single-wide bar (1). This would be printed in the barcode as: STRUCTURE OF AN INTERLEAVED 2 OF 5 BARCODEAn Interleaved 2 of 5 barcode has the following physical structure: 1. Start character, encoded as 1010. 2. Each pair of data characters

10、 is encoded (see encoding table below). 3. Stop character, encoded as 1101. INTERLEAVED 2 OF 5 ENCODING TABLEThis table indicates how to encode each digit of an Interleaved 2 of 5 barcode. Note that the encoding is expressed as N (narrow bar or space) or W (wide bar or space). ASCIICHARACTERBARCODEE

11、NCODING0NNWWN1WNNNW2NWNNW3WWNNN4NNWNW5WNWNN6NWWNN7NNNWW8WNNWN9NWNWNNOTE: The above encoding table is identical to that used with Standard 2 of 5. The only difference is that Interleaved 2 of 5 interleaves the encodings in the bars and spaces whereas Standard 2 of 5 only encodes data in the bar width

12、s. ENCODING EXAMPLEWe will now code the above example in Interleaved 2 of 5: 12345670. By this point we would already have calculated the checksum digit as 0 (the last digit of the barcode value) as illustrated in the checksum calculation section illustrated above. Now we need to encode each digit u

13、sing the encoding table above: 1. The digit 1 encoded in bars: WNNNW 2. The digit 2 encoded in spaces: NWNNW 3. The digit 3 encoded in bars: WWNNN 4. The digit 4 encoded in spaces: NNWNW 5. The digit 5 encoded in bars: WNWNN 6. The digit 6 encoded in spaces: NWWNN 7. The digit 7 encoded in bars: NNN

14、WW 8. The digit 0 encoded in spaces: NNWWN That is to say the digits 1 and 2 are encoded together, 3 and 4 are encoded together, 5 and 6 are encoded together, and 7 and 0 are encoded together. The first digit of each pair is encoded in the width of the bars and the second digit of each pair is encod

15、ed in the width of the spaces. For example, in the case of the first two digits 12, we encode the 1 in the bars using the sequence WNNNW (Wide bar, narrow bar, narrow bar, narrow bar, wide bar). We encode the 2 in the spaces that separate the bars of the first digit. The digit 2 is encoded in spaces

16、 with the sequence NWNNW (narrow space, wide space, narrow space, narrow space, wide space). Assuming 1 is a narrow bar, 11 is a wide bar, 0 is a narrow space, and 00 is a wide space, the above would be encoded as follows: BARSPACEBARSPACEBARSPACEBARSPACEBARSPACEWNNWNNNNWW11010010101100Thus encoding

17、 the first two data digits results in the sequence . In other words, a wide bar, a narrow space, a narrow bar, a wide space, a narrow bar, a narrow space, a narrow bar, a narrow space, a wide bar, a wide space. The process for the rest of the pairs of characters is the same. It results in the following: 1. START CODE (always the same): 1010. 2. 1st and 2nd Digits: . 3.