#!/usr/bin/env python3
"""Align an edited plate's figure bbox to the original plate's figure bbox.
Image-edit models redraw the figure at their own scale/offset; the projection bake
assumes the original framing, so misalignment = body sampling background (the v2
black-shard failure, 2026-07-18). Usage: align_plate.py original edited out"""
import sys
from PIL import Image

def bbox(img, thresh=28):
    g = img.convert('RGB')
    px = g.load()
    w, h = g.size
    corner = px[2, 2]
    xs, ys = [], []
    for y in range(0, h, 2):
        for x in range(0, w, 2):
            p = px[x, y]
            if sum(abs(p[i] - corner[i]) for i in range(3)) > thresh * 3:
                xs.append(x); ys.append(y)
    return min(xs), min(ys), max(xs), max(ys)

orig, edit, out = sys.argv[1], sys.argv[2], sys.argv[3]
o, e = Image.open(orig), Image.open(edit).convert('RGB')
ob, eb = bbox(o), bbox(e)
ow, oh = ob[2]-ob[0], ob[3]-ob[1]
ew, eh = eb[2]-eb[0], eb[3]-eb[1]
s = min(ow/ew, oh/eh)                       # uniform scale, height-fit
fig = e.crop(eb).resize((round(ew*s), round(eh*s)), Image.LANCZOS)
bg = e.getpixel((2, 2))
canvas = Image.new('RGB', o.size, bg)
# anchor: match bbox centers horizontally, bottoms vertically (feet stay planted)
cx = (ob[0]+ob[2])//2 - fig.width//2
canvas.paste(fig, (cx, ob[3]-fig.height))
canvas.save(out)
print(f'orig bbox {ob} edit bbox {eb} scale {s:.3f} -> {out}')