clean noise from an image

Question

I need to know how to clean noise from an image with Matlab.

lets look at this example:

Answer 1

I think there are two things you could aim to do to make them more detectable:

1. Remove patches smaller than a certain number of pixels (this would remove the spots between the sets of digits)
2. Numbers should be "closed" forms, so you need an algorithm to detect the pixels (at the top of each number) that should be changed to black in order to "close" the number "shapes".

You also have linear features that are a part of the noise signal which could be detected through edge / line detection.

Detecting contiguous "zones" and calculating characteristics such as compactness or length / height might also help in identifying which structures to keep...