How to use ImageJ to implement character recognition base on Freeman Chain Code?

Hello.I'm a beginner of JAVA and ImageJ, please take character "a" for example.(I have known the principles of Freeman chain code)

You've provided little to no context insofar as what you need, so all I can do is guess that you want ImageJ to do OCR, which as far as I know it does not.

yeah,it's OCR, but I do not know how to implement it in ImageJ, how can images become thined binary image and how to program