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maziggy
86bd9e1bd4
Follow-ups after merging PR #3128 (with the #2990 preview work): - PDF preview failed on every browser without Map.prototype.getOrInsertComputed (Chrome < 145, Firefox < 144, older Safari): "This file cannot be previewed" for any PDF. Load pdf.js's legacy build, which bundles the polyfills for page and worker, and bundle the worker through Vite (?worker&url) so build.target lowers its class static block for Safari 16.0-16.3. The browser-baseline check only scanned .js output and never saw the copied .mjs worker; it scans .mjs too. - PDF grid thumbnails only existed after someone opened the preview. Page one is now rendered server-side with PDFium (pypdfium2, new dependency, prebuilt wheels for every shipped platform) on upload, ZIP extraction and external-folder scans; Generate Thumbnails backfills PDFs as well. Renders are serialised behind a lock (PDFium is not thread-safe), run off the event loop, and scale from the page size so a huge MediaBox cannot allocate a huge bitmap. Unreadable PDFs land without a thumbnail and keep the browser fallback. - A large STEP file takes over a minute to mesh in the browser and showed only a spinner. STEP loads now show "Converting STEP model... N s" and a note that large files can take a minute or more, in all 15 locales. - Drop the two occt-import-js "externalized for browser compatibility" build warnings (path/crypto are only required in its Node branch); any other externalization still shows.
73 lines
2.9 KiB
Python
73 lines
2.9 KiB
Python
"""PDF Thumbnail Generation Service.
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Renders the first page of a PDF with PDFium (pypdfium2) so a library PDF gets
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its grid thumbnail at upload/scan time. Before this, PDF thumbnails only
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existed once somebody had opened the in-browser preview, which posted its
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first render back (#2976); that route stays as the fallback for a PDF this
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renderer cannot read.
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"""
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import logging
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import threading
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import uuid
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from pathlib import Path
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logger = logging.getLogger(__name__)
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# PDFium is not thread-safe, and callers run this through asyncio.to_thread,
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# so two uploads landing together would otherwise enter it concurrently.
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_PDFIUM_LOCK = threading.Lock()
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# Rendered at twice the output size and downsampled, so small print on the
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# page stays legible instead of breaking up into aliased specks.
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_SUPERSAMPLE = 2
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def generate_pdf_thumbnail(pdf_path: Path, thumbnails_dir: Path, size: int = 256) -> str | None:
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"""Render page one of a PDF into a square, white-backed PNG thumbnail.
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Same shape as the thumbnail the browser preview posts back (a ``size``
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square with the page centred on white), so a grid mixing both kinds
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looks uniform. Returns the thumbnail path, or None if the file cannot be
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rendered - an encrypted, empty or damaged PDF simply gets no thumbnail.
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"""
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try:
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import pypdfium2 as pdfium
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from PIL import Image
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except ImportError:
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logger.warning("pypdfium2 not installed, skipping PDF thumbnail for %s", pdf_path.name)
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return None
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try:
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with _PDFIUM_LOCK:
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pdf = pdfium.PdfDocument(str(pdf_path))
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try:
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if len(pdf) == 0:
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return None
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page = pdf[0]
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try:
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width, height = page.get_size()
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if width <= 0 or height <= 0:
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return None
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# Scale from the page's own size, so the bitmap is bounded
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# by the output size whatever MediaBox the file declares.
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scale = (size * _SUPERSAMPLE) / max(width, height)
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rendered = page.render(scale=scale).to_pil()
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finally:
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page.close()
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finally:
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pdf.close()
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rendered = rendered.convert("RGB")
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rendered.thumbnail((size, size), Image.Resampling.LANCZOS)
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thumbnail = Image.new("RGB", (size, size), (255, 255, 255))
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thumbnail.paste(rendered, ((size - rendered.width) // 2, (size - rendered.height) // 2))
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thumb_filename = f"{uuid.uuid4().hex}.png"
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thumb_path = thumbnails_dir / thumb_filename # SEC-PATH-OK: thumb_filename = uuid.uuid4().hex + ".png"
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thumbnail.save(thumb_path, "PNG", optimize=True)
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return str(thumb_path)
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except Exception as e:
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logger.warning("Failed to create PDF thumbnail for %s: %s", pdf_path.name, e)
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return None
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