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Lecture 3: Sampling and Aliasing (12)
TonyLianLong

A more in-depth definition from Wikipedia for Jaggies: "Jaggies" is the informal name for artifacts in raster images, most frequently from aliasing, which in turn is often caused by non-linear mixing effects producing high-frequency components, or missing or poor anti-aliasing filtering prior to sampling.

TonyLianLong

Aliasing is closely related to the concept of Nyquist rate, which is twice the upper cutoff frequency in the signal. Sampling below the Nyquist rate will cause multiple possible reconstructions of the original signal. More about undersampling can be found at: https://en.wikipedia.org/wiki/Undersampling

Staffethanweber

Thanks for the elaboration @TonyLianLong! Can anyone comment on the differences between jaggies and Moire artifacts? Given the same sampling scheme, what signals would lead to jaggies versus Moire?

sha-moose

As far as I understand, jaggies occur when undersampling in the spatial domain, and moire patterns occur when undersampling in the frequency domain. Thus, you're more likely to get jaggies when your image changes faster than there are pixels to accommodate (like a sharp triangle), and you'll get moire patterns if your image shifts at a high frequency (like a checkered pattern).

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