fsim — IMGMETRICS perceptual op

• Data kinds: image2d × image2d → scalar

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

Usage

FSIM (luminance only, 1 = identical, higher is better). It agrees with TID2013's FSIM.txt to 4 digits when given a Y′ limited grayscale image (iqatid.tid2013_evaluate(root, fsim, luma="limited_u8"), 3,000 pairs, max |diff| 5.0e-5). Details: fsim_pair.

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)

fsimc · fsim_pair · gmsd · 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.