Bright-background photos/renders and a tiny app icon were flagged as
AI-generated by the visible detectors. Two failure modes:
- Gemini sparkle on a bright background (snow+sky photo, white product
render) scored ~0.51. The FP gate only demoted on a low core-ring
brightness margin, which a bright background makes high. Add a gradient
floor (_SPARKLE_FP_GRAD 0.55): a real sparkle is a crisp star (grad
~0.97-1.0), a smooth luminance blob that NCC-matches the diamond is not
(the two FPs measured grad 0.105 / 0.463). The OR is a strict superset
of the old margin-only demotion, so it cannot regress dark/mid (kept by
margin) or white-bg (kept by confidence) real sparkles.
- A 48x48 geometric icon matched the Doubao/Jimeng CJK silhouette at
0.41/0.47 NCC. Purely a small-size artifact (the same icon at >=256px
collapses to ~0.06-0.10). Guard text-mark detection below a 200px short
side (_MIN_DETECT_SHORT_SIDE); real marks ship on full-resolution
renders (smallest captured sample 1086px).
Corpus re-sweep flips only OpenAI content and already-cleaned outputs,
all sub-0.5, so no provenance verdict changes. Add synthetic regression
fixtures for both modes; docs/module-internals.md updated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
New samsung_engine.py mirrors the jimeng engine but anchors bottom-left; wired
into watermark_registry, the CLI (--mark samsung / auto), and identify
(visible_samsung, medium). visible_alpha_solve.py gains a corner=bl mode;
samsung_alpha.png solved from @f-liva's flat captures. Calibrated for the
Italian "Contenuti generati dall'AI" variant. Flat black/gray/white captures
committed, real photos gitignored. Tests + docs.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Victor Kuznetsov