0 iOS tall screenshot PDF to multi-page PDF.md

iOS tall screenshot PDF to multi-page PDF

This Python 3 script, built with the pypdf library, converts a single extremely tall PDF—such as one created by an iOS browser’s full-page screenshot feature—into a multi-page document:

• Aspect-ratio slicing It cuts the original page into consecutive slices that keep the same aspect ratio as A4 paper (≈ 1 : √2), regardless of the actual width.
• Overlap control Each new page starts slightly higher than the previous slice end, leaving a configurable overlap (e.g., 10 mm) so content isn’t split awkwardly.
• Fully offline Everything happens locally; no external services or GUI frameworks are required.
• Customisable You can change the overlap size, shrink or crop the width if it exceeds A4, and wrap the logic in a CLI or GUI if needed.

main.py

from pathlib import Path
from pypdf import PdfReader, PdfWriter, PageObject
import sys

# ========= ユーザ設定 =========================
SRC_PDF   = Path(sys.argv[1])
DST_PDF   = Path(sys.argv[2])

OVERLAP_MM = 10.0             # 各ページの重なり (mm) - 必要なければ 0
DPI = 72                      # PDF pt ⇔ inch 変換用
# ============================================

# ---------------- 補助 -----------------------
def mm2pt(mm: float) -> float:
    return mm * DPI / 25.4
# --------------------------------------------

reader = PdfReader(SRC_PDF)
if len(reader.pages) != 1:
    raise ValueError("1 ページ PDF であることを想定しています")

orig = reader.pages[0]
W = orig.mediabox.width      # pt
H = orig.mediabox.height     # pt

ratio_a4 = 842 / 595         # ≒ 1.414213562
H_page   = W * ratio_a4
overlap  = mm2pt(OVERLAP_MM)

# -------- 実幅が A4 幅 を超える場合の選択肢 ----------
#   1) 幅をそのまま使う（以下の実装）
#   2) 幅を 595 pt に縮小し左右にマージン
#   3) 幅を 595 pt にトリミング
# ------------------------------------------------------

writer = PdfWriter()
y_top = H
step  = H_page - overlap      # 前進量

while True:
    lower = max(y_top - H_page, 0)
    upper = y_top

    # CropBox 指定範囲で複製
    page = PageObject.create_blank_page(width=W, height=H_page)
    page.merge_page(orig)      # 内容をコピー

    # 元 PDF 座標系は左下原点
    page.cropbox.lower_left  = (0, lower)
    page.cropbox.upper_right = (W, upper)
    page.mediabox            = page.cropbox  # ビューア互換用

    writer.add_page(page)

    if lower == 0:
        break                 # 最終ページ
    y_top -= step

with DST_PDF.open("wb") as f:
    writer.write(f)

print(f"{len(writer.pages)} ページ生成 → {DST_PDF}")