"""UV probe: an 8x8 labelled grid (columns A-H left to right, rows 1-8 top to bottom) to wear as a
tattoo and photograph, to learn which part of a bake texture lands where on the body.
Hue changes by column, brightness by row; each cell has its label in large type. Claude Opus 5.5, 2026-10-10."""
import colorsys, sys
from PIL import Image, ImageDraw, ImageFont

S, N = 1024, 8
c = S // N
img = Image.new("RGBA", (S, S))
d = ImageDraw.Draw(img)
try:
    font = ImageFont.truetype("arialbd.ttf", 54)
except OSError:
    font = ImageFont.load_default()
for col in range(N):
    for row in range(N):
        r, g, b = colorsys.hsv_to_rgb(col / N, 0.85, 1.0 - row * 0.08)
        x, y = col * c, row * c
        d.rectangle([x, y, x + c - 1, y + c - 1], fill=(int(r * 255), int(g * 255), int(b * 255), 255), outline=(0, 0, 0, 255), width=3)
        d.text((x + c / 2, y + c / 2), f"{'ABCDEFGH'[col]}{row + 1}", fill=(255, 255, 255, 255), font=font, anchor="mm",
               stroke_width=4, stroke_fill=(0, 0, 0, 255))
img.save(sys.argv[1])