I did an experiment with speckle-removal in a Poser Firefly “toon lines only” render. One of the problems of that special kind of render is, the closer you go in with the camera, the more speckles. Until a character can look like they have the measles. Using a Poser script to auto-remove all bump-maps often solves most of the problem, but not always and not entirely.
Anyway: I rendered and took the render into a leading vectorizer, Vextractor 7.x. I had found that this has a useful and very easy ‘remove isolated spots’ filter, of the sort needed after scanning hand-drawn line-art. If a spot has x number of empty/white pixels around it, it’s removed.
This works on the above very subtle example. But the problem is that the lineart produced is then inferior to what you would get from the other non-vectorising method, which involves the free Paint.NET and two free plugins.
But it occurs to me now that, back in the day, Poser’s Firefly lineart speckles were not considered a problem — because it was thought that people would vectorise the lineart and thus be able to easily clean off the specks. If you’re doing animation, this may well still be viable. In a 30 FPS cartoon seen across a living-room, that vector line ugly-fication is going to be far less noticable. But it’s not much good for comics.
So the best method for comics is Paint.NET and it’s wholly free and should run on Windows back to XP. But… it’s Paint.NET and not Photoshop. So I took another look for such a ‘remove stray pixels’ filter in Photoshop, something that would be very useful for automation of the whole process. But nothing in that line has appeared since my last such search. There are zillions of photographer plugins for correcting grain and ‘hot pixels’ on the camera sensor, but nothing for this ‘scan artwork and clean’ task. The native ‘Median’ and ‘Dust and Scratches’ are useless because they nibble into or erode the fine lineart from Poser, and lack sensitivity.
What’s needed is a computational plugin solution that says… “that dot can be deleted, because it has only white all around it and its diameter is 2 pixels or less”. The free G’MIC might have the capability to build that, but I don’t see anything there at present.