US Passport Image to German Passport Image

make_passport_sheet.py

#!/usr/bin/env python3
"""
make_passport_sheet.py

Create a 10 × 15 cm print sheet containing six German-passport-size photos
(35 mm × 45 mm) from a square 2 × 2-inch source image.

Usage:
    python make_passport_sheet.py input.jpg output.jpg --dpi 300
"""

import argparse
from pathlib import Path
from math import floor
from PIL import Image

# ----------------------------- constants -----------------------------
MM_PER_IN   = 25.4
PASS_MM_W   = 35          # passport width  mm
PASS_MM_H   = 45          # passport height mm
SHEET_MM_W  = 100         # sheet width     mm (10 cm)
SHEET_MM_H  = 150         # sheet height    mm (15 cm)
COLS, ROWS  = 2, 3        # we can fit 2 × 3 = 6 photos

# ---------------------------------------------------------------------

def mm_to_px(mm: float, dpi: int) -> int:
    """Convert millimetres to integer pixels at the given dpi."""
    return round(mm * dpi / MM_PER_IN)

def crop_to_passport_aspect(img: Image.Image) -> Image.Image:
    """Center-crop the image to the 7:9 (35:45) aspect ratio."""
    w, h      = img.size
    target_ar = PASS_MM_W / PASS_MM_H               # 0.777…
    current_ar= w / h

    if current_ar > target_ar:                      # too wide → crop sides
        new_w = round(h * target_ar)
        left  = (w - new_w) // 2
        box   = (left, 0, left + new_w, h)
    else:                                           # too tall → crop top/bottom
        new_h = round(w / target_ar)
        top   = (h - new_h) // 2
        box   = (0, top, w, top + new_h)

    return img.crop(box)

def build_sheet(cropped: Image.Image, dpi: int) -> Image.Image:
    """Place 6 passport-size copies on a 10 × 15 cm sheet."""
    # 1) exact pixel sizes
    pass_px_w = mm_to_px(PASS_MM_W, dpi)
    pass_px_h = mm_to_px(PASS_MM_H, dpi)
    sheet_w   = mm_to_px(SHEET_MM_W, dpi)
    sheet_h   = mm_to_px(SHEET_MM_H, dpi)

    # 2) resize the cropped headshot
    passport = cropped.resize((pass_px_w, pass_px_h), Image.LANCZOS)

    # 3) compute equal gutter margins
    #    let Gx = horizontal gutter between columns plus 2×outer margins
    #        Gy = vertical   gutter between rows   plus 2×outer margins
    total_free_x = sheet_w - COLS * pass_px_w
    total_free_y = sheet_h - ROWS * pass_px_h
    gutter_x = total_free_x // (COLS + 1)
    gutter_y = total_free_y // (ROWS + 1)

    sheet = Image.new("RGB", (sheet_w, sheet_h), "white")

    for r in range(ROWS):
        for c in range(COLS):
            x = gutter_x + c * (pass_px_w + gutter_x)
            y = gutter_y + r * (pass_px_h + gutter_y)
            sheet.paste(passport, (x, y))

    return sheet

def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("input",  type=Path, help="source 2×2-inch image file")
    ap.add_argument("output", type=Path, help="output 10×15 cm sheet file")
    ap.add_argument("--dpi", type=int, default=300,
                    help="print resolution (default: 300 dpi)")
    args = ap.parse_args()

    # 1) read & crop
    img     = Image.open(args.input).convert("RGB")
    cropped = crop_to_passport_aspect(img)

    # 2) build sheet
    sheet = build_sheet(cropped, args.dpi)

    # 3) embed correct DPI in the saved file
    sheet.save(args.output, dpi=(args.dpi, args.dpi), quality=95)
    print(f"✅ Saved {args.output} ({COLS*ROWS} photos) at {args.dpi} dpi")

if __name__ == "__main__":
    main()