Tool to decrypt Barcode 39. Code 39 (or Code 3 of 9 or Alpha39) is a normalized barcode system which is being replaced by Code 128.
Barcode 39 - dCode
Tag(s) : Character Encoding, Image Processing
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Encryption uses an encoding table with 43 characters: the 26 capital letters, the 10 digits and some special characters (-, ., $, /, +, % and ' ' (space). The character * can appear but it does not exist, it is only used as a delimiter for start and end.
Each character has 5 black bars and 4 white bars (9 elements in total) starting with black and alternating white and black. Each band can have 2 widths: narrow or wide (generally 3 times larger), so it is possible to binarize the code (1 for thin bands, and 0 for wide bands). Also, in these 9 elements, always 3 bands are larger, hence the name of code 39.
A barcode 39 starts with * and ends with *. Here is the character map:
Each character has 5 black bars and 4 white bars (9 elements in total), it is therefore possible to binarize the (1, 11 or 111 for black bands according to its width, 0, 00 or 000 for white bands). In these 9 elements there are 3 which are larger (between 2 and 3 times as wide) and 6 thinner. The code starts with * and ends with *.
Decryption requires to perform a reading of the bar according to EAN-128 standard.
Many app for smartphones or laser handshowers facilitate this work.
Example: The message is 101101011 111100110 010110111 011101101 111100110 011100111 101101011, check 101101011 at the beginning and the end to confirm it's a code 39 barcode. The replacement of each 9-bit group by their associated character in the table. Barcode value is DCODE.
Checksum is missing in this example
The barcode has a classic graphical form (black and white lines) or a binary equivalent (1 or B for black and 0 or W for white lines).
The barcode may have a variable length. It begins and ends with the character *.
The bar code consists of lines in groups of 9 which 3 are wider, hence the name 3 of 9 or 39.