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The two source files you referenced were indeed the ones I was looking at when I made the correction. Sinc is already defined with \pi multiplier. If you insert \pi again in the sinc formula, it will become sin (\pi^2 x)/(\pi^2 x). I tried that formula before and it led to disastrous results, which is why I made the correction to the formula in question.

EDIT: since the filter code for the two ImageMagick and MPV are buried beneath many abstractions, I searched and found another implementation that is more direct: https://github.com/python-pillow/Pillow/blob/main/src/libImaging/Resample.c#L74 . It indeed shows that π is multiplied only once as part of the definition of sinc function, and the argument of sinc function does not contain π. Syockit ( talk) 01:45, 5 February 2024 (UTC) reply

I see your point, I wasn't familiar with the convention of defining sinc as sin(pi*x)/(pi*x). If you want, you can revert my change. Tmoyar ( talk) 18:57, 8 February 2024 (UTC) reply

Thank you! Will do so! Syockit ( talk) 00:18, 10 February 2024 (UTC) reply