Hello sir,
It is not such a big program that you need to use c programmer and spend hundreds of dollar.. Plus, unless you want it to run on server, PHP is no good at creating such app. The best option here is to use javascript to generate text based images. The good thing about javascript app is that you can run it in your simple internet browser to get the files you want. Plus, you can also convert it easily in to android app if you want. Also, as any developer would know javascript it would be cost effective and easy to upgrade your app functionality in future.
Here's what you get if I do:
1.I know c-programming, javascript and php so I can deliver you the app in which ever language you want. But, the best as I have already said seems to be javascript for you.
2. I will create app that is flexible enough to create images in any number you want. For eg.
if you enter 789 to 34049, then it will create those images.
2. I am also a good designer so I will design good looking user interface for your app.
Please, allow me to handle your project. I assure you that I won't disappoint you.. Thanks..