"""Rebuild a neutral 2K albedo from the raw MV Hebat Allah scan texture.

The underwater scan has a dead red channel (mean 17/255) and a strong blue
cast, so a white balance only produces magenta noise. This script keeps the
luminance of the two live channels, stretches it, and tints it with a rust /
algae palette driven by the green-to-blue ratio. The game's fog adds the water
colour at runtime.

    python scripts/assets/hebat_allah_prepare_albedo.py <albedo_8k.png> <out_dir>

Writes albedo_2k_balanced.png and albedo_1k_balanced.png into <out_dir>.
Requires Pillow and numpy. Licence: see docs/ASSET_LICENSES.md.
"""
import sys
from pathlib import Path

import numpy as np
from PIL import Image


def balance(source: Path, out_dir: Path) -> None:
    image = Image.open(source).convert("RGB").resize((2048, 2048), Image.LANCZOS)
    rgb = np.asarray(image).astype(np.float32) / 255.0
    luminance = 0.55 * rgb[..., 1] + 0.45 * rgb[..., 2]
    low, high = np.percentile(luminance, 1), np.percentile(luminance, 99)
    luminance = np.clip((luminance - low) / (high - low), 0.0, 1.0)
    luminance = luminance ** 0.9 * 0.75 + 0.08
    algae_ratio = np.clip((rgb[..., 1] - rgb[..., 2] * 0.68) * 3.0, 0.0, 1.0)
    rust = np.array([0.62, 0.52, 0.44])
    algae = np.array([0.50, 0.58, 0.46])
    tint = rust[None, None, :] * (1.0 - algae_ratio[..., None]) + algae[None, None, :] * algae_ratio[..., None]
    out = np.clip(luminance[..., None] * tint / 0.55, 0.0, 1.0)
    result = Image.fromarray((out * 255).astype(np.uint8))
    out_dir.mkdir(parents=True, exist_ok=True)
    result.save(out_dir / "albedo_2k_balanced.png")
    result.resize((1024, 1024), Image.LANCZOS).save(out_dir / "albedo_1k_balanced.png")


if __name__ == "__main__":
    if len(sys.argv) != 3:
        sys.exit(__doc__)
    balance(Path(sys.argv[1]), Path(sys.argv[2]))