lhk229
e61fbe84f0
No colour key at all: segmentation alone drives the trimap (mode forced to 'seg', whose chroma terms degrade to no-ops on a zero background- confidence map), ViTMatte still refines the unknown band at full resolution, and pymatting still estimates edge foreground colour. Every colour-keyed stage is bypassed: background auto-detect, the directional hue split, chroma alpha suppression, despill, the cross-check veto (its suspect zone is background-hued by definition; with reuse_as_seg the second opinion still serves as the segmenter), and the unmix fallback. Guards: requires segmentation.enabled and matting_method 'vitmatte' (clear errors otherwise); despill/foreground handle model=None. Validation: flat-background default path is bit-identical pre/post (alpha and RGB |D|max = 0 on TestImage3). On a known-alpha subject composited over a gradient+blotch background, recovered alpha scores MAE 0.0018 / IoU@0.5 0.993 (0.995 with --cross-check-as-seg); the same input correctly fails auto-detection in default mode. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
62 lines
2.7 KiB
Python
62 lines
2.7 KiB
Python
from __future__ import annotations
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import numpy as np
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from .chroma import BackgroundModel
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from .deps import require_cv2
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from .settings import DespillSettings
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def despill(
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rgb: np.ndarray,
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alpha: np.ndarray,
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model: BackgroundModel | None,
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settings: DespillSettings,
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) -> tuple[np.ndarray, np.ndarray]:
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"""Remove background-colour spill from the foreground.
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The background's Lab a*/b* vector gives a chroma direction; foreground chroma
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projecting along it beyond a margin is treated as spill and pulled back toward
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neutral, keeping luminance so hair texture and shading survive. This works for
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any flat background: a saturated primary (green/blue screen) reduces to classic
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channel suppression, while low-chroma pastels -- where no single RGB channel
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dominates -- are handled by the same projection.
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Returns the corrected RGB (uint8) and the per-pixel despill weight (float32).
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"""
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# model is None with chroma disabled: no key colour means no spill direction.
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if not settings.enabled or model is None:
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return rgb.copy(), np.zeros(alpha.shape, dtype=np.float32)
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bg_lab = np.asarray(model.lab_center, dtype=np.float32)
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va, vb = float(bg_lab[1]), float(bg_lab[2])
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mag = float(np.hypot(va, vb))
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if mag < 1e-3: # near-neutral background: no chroma direction, nothing to despill
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return rgb.copy(), np.zeros(alpha.shape, dtype=np.float32)
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da, db = va / mag, vb / mag
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cv2 = require_cv2()
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rgb_f = rgb.astype(np.float32) / 255.0
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foreground = alpha > settings.edge_low
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if settings.edge_expand_radius > 0:
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radius = settings.edge_expand_radius
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kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (radius * 2 + 1, radius * 2 + 1))
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foreground = cv2.dilate(foreground.astype(np.uint8), kernel).astype(bool)
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lab = cv2.cvtColor(rgb_f, cv2.COLOR_RGB2LAB)
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A, B = lab[..., 1], lab[..., 2]
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proj = A * da + B * db # chroma toward the background hue
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excess = np.maximum(proj - settings.color_margin_lab, 0.0)
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# Full strength across the opaque range; ease off only where mostly transparent.
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alpha_weight = np.maximum(np.clip(alpha * 2.0, 0.0, 1.0), settings.alpha_weight_floor)
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color_weight = np.clip(excess / max(settings.color_margin_lab * 8.0, 1e-6), 0.0, 1.0)
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mask = foreground.astype(np.float32) * alpha_weight * color_weight
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reduce = excess * mask * settings.strength # pull chroma back along the bg axis
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lab_out = lab.copy()
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lab_out[..., 1] = A - reduce * da
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lab_out[..., 2] = B - reduce * db
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out = cv2.cvtColor(lab_out, cv2.COLOR_LAB2RGB)
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return np.clip(out * 255.0, 0, 255).astype(np.uint8), mask.astype(np.float32)
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