Vitalyvorobyev Ringgrid Tests Synthetic Fixtures

name: tests-synthetic-fixtures description: Use this to create deterministic test images/signals with known subpixel ground truth (edges, stripes, circles). Helps lock correctness before optimizing.

Synthetic fixtures (deterministic)

Principles

• Deterministic by default (no RNG), or seeded RNG only.

• Tests should check:

  • geometry error (px)
  • stability under small noise/blur
  • edge cases (odd sizes, borders, ROI truncation)

Useful fixtures

• Half-plane step edge with known line equation (slanted edge):

  • I(p)=A if dot(n, p) < t else B
  • Optional blur along n (binomial/gaussian-ish) to make it realistic

• Stripe (laser) as difference of two steps (bright-on-dark):

  • known left/right subpixel positions → known center + width

• Circle / ring boundary (later):

  • implicit distance function d = sqrt((x-cx)^2+(y-cy)^2)-r
  • intensity from sign(d) and controlled blur

Expected-value checks

• Keep early tests loose (~0.1–0.2 px).
• Add tighter tests later (aim 0.05 px) on higher-fidelity fixtures.

Regression strategy

• When a bug appears, capture it as a small synthetic fixture.

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