Umut CANandClaude Opus 5
f46fda10cb
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
60 lines
2.0 KiB
Python
60 lines
2.0 KiB
Python
"""Read a PDF's page size back from the file — no dependency, no rendering.
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The evidence rule for page setup (spec §8.3): the sheet size a plot produced is
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what the PDF says it is, not what the layout was asked for. ``/MediaBox`` is the
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one PDF object that carries it. matplotlib and AutoCAD's DWG To PDF driver both
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write it in clear text; a PDF 1.5+ writer may put the page dictionary inside a
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FlateDecode object stream, so when the plain scan finds nothing every stream is
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inflated and searched. Anything else raises rather than guessing.
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"""
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from __future__ import annotations
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import re
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import zlib
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from pathlib import Path
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__all__ = ["PT_TO_MM", "read_mediabox"]
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#: PostScript points to millimetres.
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PT_TO_MM = 25.4 / 72.0
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_NUMBER = rb"([-+]?\d*\.?\d+)"
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_MEDIABOX_RE = re.compile(
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rb"/MediaBox\s*\[\s*"
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+ _NUMBER
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+ rb"\s+"
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+ _NUMBER
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+ rb"\s+"
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+ _NUMBER
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+ rb"\s+"
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+ _NUMBER
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+ rb"\s*\]"
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)
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_STREAM_RE = re.compile(rb"stream\r?\n(.*?)\r?\nendstream", re.DOTALL)
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def read_mediabox(path: str) -> tuple[float, float]:
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"""Return the first page ``/MediaBox`` as ``(width_mm, height_mm)``.
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Raises ``ValueError`` when the file is not a PDF or carries no MediaBox.
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``/Rotate`` is not applied: the box is reported as written.
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"""
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data = Path(path).read_bytes()
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if not data.startswith(b"%PDF"):
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raise ValueError(f"read_mediabox: {path} is not a PDF (no %PDF header)")
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match = _MEDIABOX_RE.search(data)
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if match is None:
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for stream in _STREAM_RE.finditer(data):
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try:
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inflated = zlib.decompress(stream.group(1))
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except zlib.error:
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continue
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match = _MEDIABOX_RE.search(inflated)
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if match is not None:
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break
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if match is None:
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raise ValueError(f"read_mediabox: no /MediaBox found in {path}")
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x0, y0, x1, y1 = (float(value) for value in match.groups())
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return (round(abs(x1 - x0) * PT_TO_MM, 3), round(abs(y1 - y0) * PT_TO_MM, 3))
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