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#!/usr/bin/env python3
"""
utils.compositing
─────────────────────────────────────────────────────────────────────────────
Handles frame-level compositing (foreground frame + mask + background).
Public API
----------
replace_background_hq(frame_bgr, mask, background_bgr, fallback_enabled=True) → np.ndarray
"""
from __future__ import annotations
import logging
from typing import Tuple
import cv2
import numpy as np
log = logging.getLogger(__name__)
# Exception class that cv_processing.py expects
class BackgroundReplacementError(Exception):
"""Exception raised for background replacement errors"""
pass
__all__ = ["replace_background_hq", "BackgroundReplacementError"]
# ────────────────────────────────────────────────────────────────────────────
# Main entry
# ────────────────────────────────────────────────────────────────────────────
def replace_background_hq(
frame_bgr: np.ndarray,
mask: np.ndarray,
background_bgr: np.ndarray,
fallback_enabled: bool = True,
) -> np.ndarray:
"""
• Ensures background is resized to frame
• Accepts mask in {0,1} or {0,255} or float32
• Tries edge-feathered advanced blend, else simple overlay
"""
if frame_bgr is None or mask is None or background_bgr is None:
raise ValueError("Invalid input to replace_background_hq")
h, w = frame_bgr.shape[:2]
background = cv2.resize(background_bgr, (w, h), interpolation=cv2.INTER_LANCZOS4)
m = _process_mask(mask)
try:
return _advanced_composite(frame_bgr, background, m)
except Exception as e:
log.warning(f"Advanced compositing failed: {e}")
if not fallback_enabled:
raise
return _simple_composite(frame_bgr, background, m)
# ────────────────────────────────────────────────────────────────────────────
# Advanced compositor (feather + subtle colour-match)
# ────────────────────────────────────────────────────────────────────────────
def _advanced_composite(fg, bg, mask_u8):
# 1) Smooth / feather
mask = cv2.GaussianBlur(mask_u8.astype(np.float32), (5, 5), 1.0) / 255.0
mask = np.power(mask, 0.8) # shrink bleed
mask3 = mask[..., None]
# 2) Edge colour-match to reduce halo
fg_adj = _colour_match_edges(fg, bg, mask)
# 3) Blend
comp = fg_adj.astype(np.float32) * mask3 + bg.astype(np.float32) * (1 - mask3)
return np.clip(comp, 0, 255).astype(np.uint8)
def _colour_match_edges(fg, bg, alpha):
edge = cv2.Sobel(alpha, cv2.CV_32F, 1, 1, ksize=3)
edge = (np.abs(edge) > 0.05).astype(np.float32)
if not np.any(edge):
return fg
adj = fg.astype(np.float32).copy()
mix = 0.1
adj[edge > 0] = adj[edge > 0] * (1 - mix) + bg[edge > 0] * mix
return adj.astype(np.uint8)
# ────────────────────────────────────────────────────────────────────────────
# Simple fallback compositor
# ────────────────────────────────────────────────────────────────────────────
def _simple_composite(fg, bg, mask_u8):
m = mask_u8.astype(np.float32) / 255.0
m3 = m[..., None]
return (fg.astype(np.float32) * m3 + bg.astype(np.float32) * (1 - m3)).astype(np.uint8)
# ────────────────────────────────────────────────────────────────────────────
# Utilities
# ────────────────────────────────────────────────────────────────────────────
def _process_mask(mask):
"""Ensure uint8 0/255 single-channel"""
if mask.ndim == 3:
mask = cv2.cvtColor(mask, cv2.COLOR_BGR2GRAY)
if mask.dtype != np.uint8:
mask = (mask * 255).astype(np.uint8) if mask.max() <= 1 else mask.astype(np.uint8)
_, mask = cv2.threshold(mask, 127, 255, cv2.THRESH_BINARY)
return mask |