#!/usr/bin/env python3
"""Frame -> flat (RGB888 palette + index plane) blob for the MAME Lua loader.

Packing into the X68000 palette word is done Lua-side on purpose: the exact
channel order is a hardware fact we intend to CONFIRM BY EYE, not assume, so it
has to be cheap to change without regenerating the blob.
"""
import sys, struct, glob
import numpy as np
from PIL import Image

src, out = sys.argv[1], sys.argv[2]
f = sorted(glob.glob(f"{src}/*.png"))[int(sys.argv[3]) if len(sys.argv) > 3 else 0]
im = Image.open(f).convert("RGB")
W, H = im.size

q   = im.quantize(colors=256, method=Image.MEDIANCUT, dither=Image.NONE)
pal = np.array(q.getpalette()[:256*3], dtype=np.uint8).reshape(256, 3)
idx = np.asarray(q, dtype=np.uint8)

with open(out, "wb") as fh:
    fh.write(b"DLXR")
    fh.write(struct.pack(">HH", W, H))
    fh.write(pal.tobytes())
    fh.write(idx.tobytes())

# reference PNG of exactly what the X68000 should display
Image.fromarray(pal[idx]).save(out.replace(".bin", "_ref.png"))
print(f"src={f} {W}x{H} colors={len(np.unique(idx))} -> {out}")