illusion op• Data kinds: none → rgb (an op determined by its arguments alone — it takes no image or data input)
• Call: import fullseye as fs; fs.ledger.illusion_cafe_wall(size: 'int' = 40, rows: 'int' = 8, cols: 'int' = 10, mortar: 'float' = 2.0, shift: 'float' = 0.5) -> 'np.ndarray' (to call the implementation directly, import illusion; illusion.illusion_cafe_wall(size: 'int' = 40, rows: 'int' = 8, cols: 'int' = 10, mortar: 'float' = 2.0, shift: 'float' = 0.5) -> 'np.ndarray'; from the registry, opsgenerative.get("illusion_cafe_wall"))
Café wall illusion. Although the mortar lines are exactly horizontal, they look tilted.
shift is the checkerboard offset per 1 row (as a fraction of size). At an offset of 0 or 0.5 the illusion disappears -- the classic observation is that it is strongest around 0.25, and this op lets you sweep the offset directly (the reason shift=0.25 is not the default is that we do not want a generator's default to claim "maximum effect").
Invariant: the centre y of each mortar line is exactly k * size (k = 1..rows-1).
• 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.
• poc_calipers_under_illusion — py -3.11 examples/poc_calipers_under_illusion.py
rgb as input)—
illusion)illusion_muller_lyer · illusion_ponzo · illusion_zollner · illusion_poggendorff · illusion_fraser_spiral · illusion_ebbinghaus · illusion_kanizsa · illusion_checker_shadow
*Provenance: illusion.py — GENERATIVE 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.