PDF Occlusion is an Anki add-on that creates image occlusion cards directly from PDF lecture slides. No more importing one image at a time. Open any PDF (or several at once), draw boxes over what you want to memorize, and generate cards in bulk. Built for studying from slide-heavy lectures.

Quick Start

1. Go to Tools -> PDF Occlusion, or use the toolbar button in the card editor (Ctrl+Shift+P).
2. Click Open PDF — one file or several.
3. Click and drag to place boxes over the content you want to memorize, or press F and drag over a region to have them placed for you.
4. (Optional) Select multiple boxes and press G to group them into a single card region.
5. Pick a deck and click Create All Cards.

Keyboard Shortcuts

• D / V / T — Draw / Select / Text tool
• F — Detect, then drag over the area to scan
• P — Peek through the masks
• G / U — Group / ungroup selected boxes
• N — Add a note to selected box(es)
• Del / Backspace — Remove selected box(es)
• Left / Right arrow — Navigate slides (nudges selected boxes instead)
• Ctrl+A — Select all boxes on slide
• Ctrl+C / Ctrl+V — Copy / paste boxes, across slides too
• Ctrl+Z / Ctrl+Shift+Z — Undo / redo
• Ctrl+ / Ctrl- / Ctrl+0 — Zoom in / out / fit
• Ctrl+Shift+V — Cloze composer
• Ctrl+Shift+P — Open from card editor
• g — While reviewing: show all / hide all

Configuration

Tools -> Add-ons -> PDF Occlusion -> Config

• occlusion_mode — "ao" Hide All, Show One (default) or "oa" Hide One, Show One
• mask_color — RGB color of boxes not being tested (default [120, 120, 120])
• highlight_color — RGB color of the box being tested (default [131, 110, 170])
• mask_opacity — opacity of the mask rectangles on cards, 0–255 (default 255)
• editing_mask_opacity — opacity of the masks in the editor, 0–255 (default 150); at 255 a box hides its content as you draw it, and P peeks through
• show_all_shortcut — key that reveals the whole slide while reviewing (default "g", "" for none)
• render_dpi_scale — resolution multiplier for rendered pages; higher = sharper cards, more memory (default 2.0)
• default_zoom — starting zoom when a PDF opens (default "fit")
• default_deck — route new cards to a specific deck by name
• note_type_name — name of the note type to create/reuse (default "PDF Occlusion")
• add_editor_button — show or hide the toolbar button in the card editor
• close_after_creating — close the dialog automatically after cards are created

Notes

• Requires Anki 23.10 or later
• Works on macOS (Apple Silicon and Intel), Windows (x64), and Linux (x64 and ARM) — the PDF rendering library (pypdfium2) is bundled, no separate install required, on any Anki Python version
• Detect boxes a ruled table cell by cell and anything else word by word; on a picture-only slide it falls back to macOS text recognition, so that case is macOS-only
• Text-heavy slides can be made into cloze cards instead, in the same window (Ctrl+Shift+V)
• Select a card in Browse and press Ctrl+Shift+P to reopen its slide and drag its boxes; Create All Cards updates existing cards in place, leaving scheduling and review history untouched
• A PDF Occlusion note type is created automatically on first use
• Media files are cleaned up automatically when the last card referencing a slide is deleted
• Compatible with Image Occlusion Enhanced — both add-ons can run in the same profile

Source and bug reports: github.com/bananasrlowkeygood/anki-pdf-occlusion