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Two-dimensional edge packets

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9 Two-dimensional edge packets

The first image consists of a smooth background and one sharp disk. The same three logical levels must remain separate:

  1. the exact theorem using the known decomposition;

  2. a limited estimator designed for a positive-contrast two-class packet;

  3. the open problem of recovering arbitrary edge packets under noise and model ambiguity.

A disk and smooth background reconstructed with global Fourier truncation and a retained exact edge packet.
A sharp disk on a smooth background. Global Fourier truncation produces a bright boundary halo and oscillatory interior and exterior error. Retaining the exact edge packet leaves only the smooth-background approximation error.

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Numerical certificate 9.1: Two-dimensional errors

For the \(192\times192\) disk experiment, a square Fourier mask retains indices \(|k_x|,|k_y|\le16\), or \(33^2=1089\) bins. The reported errors are

\[ \begin{array}{lrr} \toprule \text{method}&\text{full-image RMSE}&\text{boundary-band RMSE}\\ \midrule \text{global Fourier truncation}&3.7643\times10^{-2}&1.8541\times10^{-1}\\ \text{known edge packet}&6.4752\times10^{-5}&1.2709\times10^{-5}\\ \text{estimated edge packet}&3.4043\times10^{-3}&8.8834\times10^{-3}\\ \bottomrule \end{array} \]

The mask intersection-over-union was one in this positive-contrast synthetic case. The amplitude was estimated rather than inserted from the generating model.

Stages of the limited two-class edge-packet estimator applied to the observed disk image.
The limited data-driven experiment. The observed image alone is thresholded into two intensity classes, cleaned topologically, harmonically filled, spectrally smoothed, and recombined with an estimated jump.

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9.1 Curves, corners, and multiple amplitudes

The exact theorem does not depend on the shape of the known edge packet. The next experiment contains a disk, a square, and a diamond with different jump amplitudes.

Known-packet reconstruction of curved, cornered and overlapping regions with different jump amplitudes.
Known-packet stress test with curved boundaries, corners, overlap, and different jump amplitudes. The exact packet is not a binary mask multiplied by one amplitude; it is the complete piecewise packet.

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Numerical certificate 9.2: Multiedge errors

The global reconstruction had RMSE \(3.3740\times10^{-2}\) and maximum error \(3.2807\times10^{-1}\). The known-packet reconstruction had only the remaining smooth-background error. The experiment checks the finite implementation of the theorem for a composite packet; it is not a data-driven multiregion segmentation result.

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