Periodic Noise

Updated 02 Oct 2026

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What it is
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  structured interference that repeats across an image, often appearing as stripes, waves, or a grid
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Frequency interpretation
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  repetition can produce concentrated peaks in the Fourier spectrum
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  real-valued periodic patterns generally produce conjugate frequency pairs
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Reduction
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  identify likely interference frequencies and attenuate them using appropriately paired notch filters.
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  preserve useful scene frequencies where possible; legitimate texture can overlap with the interference.
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Project correction
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  reduce_periodic_noise attempts to reject a square around the shifted spectrum’s center.
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  This suppresses DC and nearby low frequencies rather than locating periodic-noise peaks.
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  The parameter called radius is a square half-width.
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Boundary issue
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  the radius is not constrained by image dimensions.
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  with a $32\times32$ image and radius $30$ , negative slice indices cause the code to mask a $14\times14$ corner region while leaving DC untouched.
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  construct masks using validated bounds or frequency coordinates.
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Reference
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  https://docs.opencv.org/doc/doxygen/html/d2/d0b/tutorial_periodic_noise_removing_filter.html
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Linked references 2