#!/usr/bin/env python3
"""Trim a generated billboard down to just its poster face.

Usage: crop_poster.py <image.jpg> [more.jpg ...]

FLUX renders a billboard *in situ* -- sky, support pole, sometimes a wall --
however hard the prompt asks for the poster alone. Mapped onto a flat panel
that bakes sky into the sign. The poster is always the saturated part and the
surroundings are always washed out, so trim rows/columns whose mean saturation
falls below a fraction of the image's peak. Survives regeneration, unlike a
hand-measured crop box.
"""
import sys
from PIL import Image

FLOOR = 0.42        # keep bands at >=42% of peak row/col saturation
MIN_KEEP = 0.35     # never crop away more than 65% of a dimension


def band_keep(profile):
    peak = max(profile) or 1
    thresh = peak * FLOOR
    idx = [i for i, v in enumerate(profile) if v >= thresh]
    if not idx:
        return 0, len(profile)
    lo, hi = idx[0], idx[-1] + 1
    if (hi - lo) < len(profile) * MIN_KEEP:   # suspiciously tight -> leave it alone
        return 0, len(profile)
    return lo, hi


def crop(path):
    im = Image.open(path).convert("RGB")
    sat = im.convert("HSV").split()[1]
    w, h = im.size
    px = sat.load()
    cols = [sum(px[x, y] for y in range(0, h, 4)) for x in range(w)]
    rows = [sum(px[x, y] for x in range(0, w, 4)) for y in range(h)]
    x0, x1 = band_keep(cols)
    y0, y1 = band_keep(rows)
    out = im.crop((x0, y0, x1, y1)).resize((w, h), Image.LANCZOS)
    out.save(path, quality=90)
    print("%s: kept x %d-%d, y %d-%d of %dx%d" % (path.split("/")[-1], x0, x1, y0, y1, w, h))


for p in sys.argv[1:]:
    crop(p)