Gwyddion Flat-Disc Morphology Compatibility

Status and scope

gwyddion_filter_flat_disc_morphology records Gwyddion 2.71 Filter-tool flat-disc Opening and Closing for finite, non-empty, full-field 2D data with mask policy fixed to ignore. It is limited to the frozen 12-field campaign and sizes 2, 3, 4, 5, 30 and 31.

Reference and parameters

The reference is the audited installed Gwyddion 2.71 executable path through gwy_data_field_area_filter_min_max. size_px is an integer in 2..31; the planned public default is 5. The kernel is a K by K digital ellipse, where K equals size_px.

Numerical semantics

The exterior policy is nearest valid edge pixel. Minimum/erosion uses the unreflected RLE mask and anchor (K-1)//2; maximum/dilation uses the rotated, row-sorted RLE mask and anchor K//2. Opening is dilation after erosion; Closing is erosion after dilation.

The executable hierarchy is not generic C-language tie semantics. The audited Gwyddion 2.71 library (libgwyprocess2.so.0.51.1, SHA-256 5f5b53cb544068638d1a3be8d6703345e49d5626d3fa4791106ce11bc051d3d7, Build ID 04187a41d4102c827e2705bb867292ba77ae37f4) recursively constructs Each/Even row reductions. Its compiled MINSD/MAXSD composition sites select the second operand on equal values, preserving signed zero. The later RLE aggregation uses strict comparison and retains the earlier row-major segment.

Evidence and fixture

The external canonical reference is SHA-256 907bd347cc8c213d1061b786b6efe5692c87ffd8be62db1f6de2bd9bc78acdbd and its provenance is c3777cdcfdd868a705ef09c63a7548a5b1c0eb0b79d053e02ac2f45e9c97e5af. The independent oracle V2 is bf4129fe4fd871dda3132d5457d45d0833d69e9acd5cf3bb765fc0f3a8d9792e; its executable reduction model is 43089668a7fe0c699093be440402c8b1b11b42dfea4eb720785241788306c543.

The fixture stores 12 inputs, 30 masks for sizes 2..31, 72 Opening outputs, and 72 Closing outputs. It records kernels 30/30 and both operations 72/72 bitwise exact, max absolute difference 0, max ULP 0, signed-zero mismatches 0, and input mutation 0.

The rejected uninitialised-kernel microprobe is invalid evidence: elliptic fill writes active pixels only. Approved probes zero-initialize the kernel before filling it.

Non-claims

This is not universal equivalence. It excludes NaN, infinities, ROI, masks, ASF, tip morphology, other Gwyddion versions/builds, and performance parity. It records the audited executable path, not a claim that all C compilers lower the source identically.