rotate_bug.py

rotate_bug.py

from PIL import Image, ImageDraw, ImageFont
import pypdf
import random
import io

PAGE_W = 1240
PAGE_H = 1754

NO_ROTATE_PDF = "pdf_OK.pdf"
WITH_ROTATE_PDF = "pdf_NOK.pdf"


def render_page(number: str) -> Image.Image:
    img = Image.new("RGB", (PAGE_W, PAGE_H), "white")
    draw = ImageDraw.Draw(img)

    font = ImageFont.load_default(100)
    text = f"Number: {number}"
    bbox = draw.textbbox((0, 0), text, font=font)
    text_width = bbox[2] - bbox[0]
    x = (PAGE_W - text_width) / 2
    y = 100 - bbox[1]
    draw.text((x, y), text, fill="black", font=font)
    return img


def save_pdf(image: Image.Image, path: str, rotate: int) -> None:
    buf = io.BytesIO()
    image.save(buf, format="PDF", resolution=200.0)
    buf.seek(0)

    reader = pypdf.PdfReader(buf)
    writer = pypdf.PdfWriter()
    page = reader.pages[0]
    if rotate:
        # page.rotate() only updates the /Rotate entry in the page
        page.rotate(rotate)
    writer.add_page(page)

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


def generate_pdfs(number: str) -> None:
    """Write two visually identical PDFs that differ only in /Rotate."""
    upright = render_page(number)

    # PDF A: bitmap stored upright (1240 x 1754), no /Rotate flag.
    save_pdf(upright, NO_ROTATE_PDF, rotate=0)

    # PDF B: bitmap stored rotated 90 degrees clockwise. /Rotate 270 to rotate the page 
    sideways = upright.rotate(-90, expand=True)
    save_pdf(sideways, WITH_ROTATE_PDF, rotate=270)

number = f"{random.randint(100000, 999999)}"
generate_pdfs(number)