SYMMETRIC_ZONES
===============

Python object: ``phenotypic.schema._symmetric_zones.SYMMETRIC_ZONES``

Mask-based radial expansion measurements for colonies on solid media.

Summarises each colony's radial growth through four scalars derived
directly from the binary object mask: the inoculum core radius (shared
with ``RADIAL_EXPANSION``), the radius at which growth stops being
angularly symmetric, and mean / maximum radial extent beyond the core.

Unlike ``RADIAL_EXPANSION``, no skeletonization, branch tracing, or
runner-outlier statistics are involved — all values are computed from
per-annulus mask geometry and a circular-statistics angular resultant
length. Intended for users who care about colony-level expansion and the
symmetry of that expansion, not individual hyphae.

.. list-table:: Category: **SymZones**
   :header-rows: 1

   * - Column label
     - Description
   * - ``SymZones_CoreRadius``
     - Radius of the dense inoculum core, determined by PELT changepoint detection on the radial mask-density profile centered on the inoculum. Growth measurements are reported relative to this boundary.
   * - ``SymZones_SymmetricRadius``
     - Radial distance from the inoculum centroid at which colony growth ceases to be angularly uniform. Computed as the first radius past the core where the smoothed per-annulus circular mean resultant length of mask-boundary pixels exceeds the symmetry threshold. Equals the colony outer envelope when growth remains symmetric throughout.
   * - ``SymZones_MeanExpansion``
     - Mean distance of mask-boundary pixels from the inoculum centroid, measured from the core boundary outward. Captures the typical radial extent of growth past the inoculum, averaged over all angular directions.
   * - ``SymZones_MaxExpansion``
     - Maximum distance of any mask pixel from the inoculum centroid, measured from the core boundary outward. Captures the farthest extent of growth past the inoculum.
   * - ``SymZones_CoreEndRadius``
     - Mean radius of the inoculum core boundary derived from the per-angle bright/background ratio walk. Each of 360 1° angular sectors finds the outer edge of the contiguous core run (bright fraction >= tau_core); the reported value is the mean across sectors. Compare with CoreRadius (the global PELT changepoint) — close agreement indicates a well-formed core.
   * - ``SymZones_DenseEndRadius``
     - Mean outer radius of the dense branching zone, where mask-bright pixels dominate (bright fraction >= tau_sparse). Per-angle radii are capped at the SymmetricRadius and angularly median-smoothed before averaging.
   * - ``SymZones_SparseEndRadius``
     - Mean outer radius of the sparse branching zone (= colony envelope inside the symmetric growth front). Equals min(objmask outer envelope, SymmetricRadius) per angle, averaged across 360 sectors.
   * - ``SymZones_CoreArea``
     - Pixel^2 area of the inoculum core zone, integrated across the 360-sector polar polygon defined by the per-angle core radii.
   * - ``SymZones_DenseArea``
     - Pixel^2 area of the dense branching zone, the annular region between the per-angle core boundary and dense-branching boundary.
   * - ``SymZones_SparseArea``
     - Pixel^2 area of the sparse branching zone, the annular region between the per-angle dense boundary and the symmetric-envelope outer boundary.