how to create a customized filter for the given image?

I have to filter an image. I should not use inbuilt commands like medfilt2 etc., I have to create my own filter. Can anyone specify the method?

Answer 1

[Image Analyst]

Two or four nested for loops should do it, depending on what you want to do.

[Sivakumaran Chandrasekaran]

I can understand your answer to certain extent. I can imagine it.But I cant able to write code with this guess. It would be more better if you could explain little bit more or just 4 or 5 lines sample code

[Walter Roberson]

You have not indicated what kind of filter you are interested in, so the answer has to be vague.