I've had a couple of times when working with scanned images where the piece I need is obscured or otherwise blemished by things such as halftoning in the case of printed items or moire effects when scanning patches or pieces of cloth. Is there an effective technique for removing these visual artifacts?
I work with digital painting and coloring of hand-drawn lineart, and I have had the issue where halftoning occurs if you scan printed lines, or in some cases you get a slight artifact from the inkbleed on inked lineart or graphite smudge of pencils. In those cases, I'm trying to get a black and white representation of the lineart, so I find that using a brightness filter or manually "burning" everything to the darkest black possible unites the dots into one contiguous line.
I suspect that you're talking more about a potential aliasing issue that occurs during scanning of printed material, and there are some decent guides out there on how to deal with them programmatically, or at the very least with image editing software like photoshop. One such guide being here: Removing a Moire Pattern.
"Sometimes scanners scan a bit on the dark side or are a bit heavy on certain colors. When you scan from printed sources, a Moire pattern may appear. All of the above factors depend on which type of scanner and materials you use. In many cases, you will want to use your image as it is. But, for those occasions when an adjustment is called for, then it's time for image manipulation software. We have found Photoshop to best suit our needs. "