dichromatic oprgbimage × labels → vectorimport fullseye as fs; fs.ledger.illuminant_from_dichromatic_planes(image_rgb, labels, min_pixels=16, min_plane_ratio=1e-06, min_intersection_ratio=1e-06) (実装を直接呼ぶなら import specularity; specularity.illuminant_from_dichromatic_planes(image_rgb, labels, min_pixels=16, min_plane_ratio=1e-06, min_intersection_ratio=1e-06)、台帳から引くなら opsspecular.get("illuminant_from_dichromatic_planes"))Recover the illuminant colour from two or more materials. → unit 3-vector.
Lee’s construction (1986). Under the dichromatic model every pixel of one material lies in the plane spanned by that material’s body colour and the illuminant colour, so each material contributes a plane through the origin of RGB, and all of those planes contain the illuminant direction. Two materials with different body colours therefore intersect in exactly one line, and that line is the answer — a null-space computation, closed form.
labels is an (H, W) integer map naming the material at each pixel;
negative labels are ignored (background). Each material needs min_pixels
pixels and genuine highlight variation: a material seen with no specular
reflection at all has colours along a single ray, which defines no plane.
That is measured by the second-to-first singular ratio of its colour matrix
and rejected below min_plane_ratio rather than contributing an arbitrary
normal.
The returned direction is unit length with a positive component sum
(illuminant colours are positive; the null space fixes the line, not the
sign). On synthetic data with three known materials it reproduces the true
illuminant with a maximum component error of 4.4e-14 and an angular error
that rounds to 0.0 degrees (measured in tests/test_specularity.py).
min_intersection_ratio guards the answer itself: if the plane normals are nearly parallel — two materials whose body colours differ only in brightness, which is the same material twice — the intersection is ill-conditioned and the call raises instead of returning a direction picked by rounding error.
Raises ValueError: shape or dtype problems as in
:func:specular_diffuse_split; labels is not an (H, W) integer map
matching the image; more than :data:MAX_MATERIALS distinct labels; fewer
than two materials survive the min_pixels and min_plane_ratio tests; the
surviving planes do not intersect in a well-determined line.
py -3.11 examples/poc_white_balance.pypy -3.11 examples/specular_photometric.pyvector を入力に取れる)—
dichromatic)specular_diffuse_split · specular_coefficient_map · specular_free_transform
Provenance: specularity.py — SPECULAR operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.