how to do noise cancellation of image

i have to filter the image. can i use filter command directly. i have seen in many places that they add noise initially and then applying filter. whats the purpose of it.

Answer 1

[Image Analyst]

Evaluating how well their filter works, don't you think? The usual way to see how well your filter works it to add noise to your "perfect" image and then see how close your filtered image comes to your original perfect image. Does that make sense to you?