gmsd — IMGMETRICS perceptual op

• Data kinds: image2d × image2d → scalar

• Call: import fullseye as fs; fs.ledger.gmsd(ref, dist, data_range: 'float' = 255.0, c: 'float' = 170.0) -> 'float' (to call the implementation directly, import iqafsim; iqafsim.gmsd(ref, dist, data_range: 'float' = 255.0, c: 'float' = 170.0) -> 'float'; from the registry, opsimgmetrics.get("gmsd"))

Usage

GMSD = standard deviation of the GMS map (N−1, the original implementation's std2, Eq. 5 of the paper). 0 = identical, larger means more degraded (lower is better — the rank correlation with MOS is negative, and published tables report |ρ|: TID2013 overall |SROCC| 0.8038, secondary source 0.8044). Input (H, W) or (H, W, 3) (3-ch uses Y). iqatid.tid2013_evaluate(root, gmsd, luma="rgb"). Raises ValueError: same as gmsd_map, or the map is 1 pixel (variance undefined).

Detailed usage guide

• image_difference_metrics family guide

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• poc_iqa_fsim_gmsd_vif — py -3.11 examples/poc_iqa_fsim_gmsd_vif.py

Ops the type connects to (they accept scalar as input)

luma_limited_u8 · rank_data · tid2013_index

Same category (perceptual)

fsim · fsimc · fsim_pair · gmsd_map · vifp · phase_congruency_pc

*Provenance: iqafsim.py — IMGMETRICS operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.