Moiré no more (2021)
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Moiré no more (2021)
1–10 of 34 posts
Re: Moiré no more (2021)
#2Past discussion: https://news.ycombinator.com/item?id=28663719
Relevant xkcd: https://xkcd.com/1814/
Re: Moiré no more (2021)
#3> All the demoireing guides tell you to apply a sharpening filter after this to compensate, but that’s like reheating cold pizza. You will never get back to where you were before, no matter how hard you try
Actually the noise from the moire can fake detail that wasn't there in the first place. Put film grain or a raster on top of a blurry image and it will subjectively improve in quality.
Re: Moiré no more (2021)
#4A certain YouTube creator wears striped shirts on camera a lot, but I feel like he should probably know better. I wonder if it’s an intentional, subtle troll?
Re: Moiré no more (2021)
#5I wonder what would be the more systematic approach than manually painting over the fft image? That constellation of peaks in fft should be reasonably easy to recognize (semi-)automatically, then you'd need to figure out good mask for those.. is it a circular blob, or maybe diamond/star shape? And what size is best? Etc etc.
Re: Moiré no more (2021)
#6A certain YouTube creator wears striped shirts on camera a lot, but I feel like he should probably know better. I wonder if it’s an intentional, subtle troll?
What's the point of your comment without naming him?
Re: Moiré no more (2021)
#7Past discussion: https://news.ycombinator.com/item?id=28663719 Relevant xkcd: https://xkcd.com/1814/
Ah, thanks. I did search before submitting but nothing came up at the time (must have been my connection).
Re: Moiré no more (2021)
#8When you get Moiré from the sensor of a camera or scanner, then there is nothing much you can do.
But extreme Moiré effect from resizing is not really Moiré. It's aliasing. And it typically happens because the resizing happens in a non-linear colorspace and/or with a poor kernel. Unfortunately this mistake is quite common in many image processing software.
Re: Moiré no more (2021)
#9I wonder what would be the more systematic approach than manually painting over the fft image? That constellation of peaks in fft should be reasonably easy to recognize (semi-)automatically, then you'd need to figure out good mask for those.. is it a circular blob, or maybe diamond/star shape? And what size is best? Etc etc.
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Re: Moiré no more (2021)
#10I wonder what would be the more systematic approach than manually painting over the fft image? That constellation of peaks in fft should be reasonably easy to recognize (semi-)automatically, then you'd need to figure out good mask for those.. is it a circular blob, or maybe diamond/star shape? And what size is best? Etc etc.
It has been a long time since I have done anything in this domain (20+ years), but if I understand correctly, the original article author is essentially filtering out high frequency signals by painting over the bright FFT spots, essentially creating a localized low-pass filter or maybe band-pass filter.
FFT essentially just transforms data into its frequency domain, so I assume the representation shown in the article is just that, brighter spots indicate higher frequency information (which would come from all the little spaced dots), so killing those essentially smooths the noise out of the data.
I imagine that the same effect could be automatically achieved by identifying which frequencies to filter out to get the desired effect.