When is a barcode not a barcode?

Have you ever looked at the back of a driver's license and wondered what that weird looking barcode is? Well, my strange brain is always inquisitive and the other day I was looking at mine and decided to see if I could take a photo of it and get the data from it. 

The first thing to do was to work out the format of the barcode. This was where I found that it isn't actually a barcode. It is a special type of pdf called PDF417. PDF417 was developed in 1991 by Dr. Ynjiun P. Wang. I could bore you with the format of PDF417, but really the PDF417 symbol consists of 3 to 90 rows.

So now I knew what I was dealing with, how was I going to pull it apart? First I needed to know if there was a third party library out there that can read PDF417. I was in luck ZXing.NET has a library that can read bar codes. It can also read PDF417!!! Eureka, I was one step closer.

Being a .Net geek I wired up Visual studio. Made a quick console app. Imported the ZXing package and started to play. Oh and to make it more fun I am using .Net 10. So let's dive in...

First the NuGet Packages. Notice I need the ZXing.Net.Binding.Windows.Compatibilty, that's because I'm using .Net 10!!!



Now to the meat of the console app.
I first want to get the text from the "barcode". I will create a method for this.

First I turn the image of my license into a bitmap. Next I set up the ZXing reader and tell it that I want to get a PDF417 symbol. I then try to decode the bitmap of my license. What this does is the ZXing Barcode Reader searched the bitmp to see if it can find a PDF417 symbol. If so it decodes it. Finally it return all the text from the decoded symbol.

Great, we have a decoder method. Now we need to break apart the text from the symbol. Let's create a method for that.


I am going to read each line of the decoded symbol. Notice that I am only interested in lines that start with character D and are at least 3 characters long. That is because these lines contain the juicy data from the license.

So, what are some of the interesting data that we might be interested in?

DAQ - Driver License Number
DBD - Date License Was Issued
DBA - Date License Expires
DAC - First Name
DAD - Middle Name
DCS - Last Name
DBB - Date Of Birth
DAY - Color of Eyes
DAU - Height in Inches - even though the license shows it in feet and inches. Some show it in Height and Inches
DAG - Street Address
DAI - City
DAJ - State

These aren't all of them and note every jurisdiction is the same, but these are the most common. If you want all of them Google AAMVA DL/ID Card Design Standard. So now we have a method to decode the license and one to extract the juicy data let's get some of it.

So, first I decode, then I extract the data and then I grab some of the things I want. So, lets see the result.....


Obviously if I was writing an identity systems I might want to store the driver license number. If so, I would suggest hashing it.

NOW THE DISCLAIMER
In order to use someone's driver license you must first get their permission. Also, only store what you need for your system. 

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Thanks for viewing my blob post. Hopefully it can be of use to you sometime. If you want the source code for this blog please drop me a line admin@sadold.dad and I will be happy to send it to you. As always if you want me to write a blog on some tech stuff drop me a line.









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