Craigslist Captcha Image Cleanup

I have a working craigslist captcha decoder however I do not have the source code to clean up the image prior to feeding it to the ocr. The clean up code is to be done using the aforge imaging library. I will provide you with the ocr code to read the image once the image has been cleaned up. I will also provide you with an image before cleanup and one after cleanup so you may determine which filters to use. I'm only interested in developers who have already completed this task before. Thank you.