Captcha - TPG - Part 1

Today, I was planning to change my internet to unlimited with TPG. To my surprise it will take 3 weeks to completed, it was disappointing. The cool thing is that TPG captcha look really cool, so we are going to crack it.
For a live demo go here.
https://cyberstore.tpg.com.au/register/homephone/images/generateimage.php

Feature of this captcha:

• Random rotation
• Random character and numbers
• Random Font
• Fix background distortion
• Random circle background distortion

This is a good captcha, but it not a great captcha, to be great it need a bit more work

• Random font size
• Tilting of image vertical and horisontal
• Random width for circle background distortion

Luckly for us they didn't have any of the three missing feature.
The first step is to remove the background like below.

 The image was clean using python with python image library. What happen is that each pixcel are compare with it surrounding, the ones with not so much surrounding are remove.

The next step is to identify the character, it a bit tricky, the approach I'm using is assist learning for the programs. The program is going to get a set of captcha and link the same character together. Since the captch don't know what the character are, we have to let it know watch each picture mean. This will involve assigning 26 character and 10 digit.

Stay tune for part 2, I'll go into more detail for identify the characters, and some cool method to hack chaptcha that are distorted via tilting.