DK Scraper

Downloads pages from Digitální Knihovna as numbered PNG files. Available as a Chrome extension (recommended) or a browser console script.

Warning: Only works on documents accessible with your current login — e.g. via university library access. DO NOT distribute downloaded pages. The scraper just automates what would otherwise take hours of manual screenshots.

Note: Digitální Knihovna servers can be slow or unresponsive, and your login session may drop mid-run. If the scraper stalls or stops, just restart it from the last successfully downloaded page.

Output: Individual PNG files (page_0001.png, ...). To combine them into a PDF, use merge_pngs_to_pdf.py.

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Chrome Extension (recommended)

Installation

1. Open Chrome and go to chrome://extensions/
2. Enable Developer mode (top right toggle)
3. Click Load unpacked and select the chrome_extension/ folder

Usage

1. Open a book in Digitální Knihovna
2. Click the DK Scraper extension icon
3. Set Start page (default: 1) and optionally Total pages (leave blank to download all)
4. Click Start — pages will be saved to your Downloads folder as page_0001.png, page_0002.png, etc.
5. Click Stop at any time to abort

The popup shows live status (Running — page N…) and updates automatically when the run finishes.

Double-page spreads are saved as two files per spread: page_0001_a.png and page_0001_b.png. Therefore page number you choose should represent numbered page of the last file you downloaded.

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Merge PNGs into PDF

The helper script merge_pngs_to_pdf.py merges downloaded page_*.png files into one PDF.

Install the Python dependency once:

python3 -m pip install Pillow

From the folder containing the downloaded PNG files, run:

python3 /path/to/digitalni\ knihovna\ scraper/merge_pngs_to_pdf.py -o output.pdf

By default, the script removes empty scanner background around each page. This is useful for double-page spread files such as page_0001_a.png and page_0001_b.png, where one side can contain only empty black/white background.

Additional crop modes:

# exact 50% split: a keeps the left half, b keeps the right half
python3 /path/to/digitalni\ knihovna\ scraper/merge_pngs_to_pdf.py --crop-mode half -o output.pdf

# no cropping
python3 /path/to/digitalni\ knihovna\ scraper/merge_pngs_to_pdf.py --crop-mode none -o output.pdf

# keep more border around detected content
python3 /path/to/digitalni\ knihovna\ scraper/merge_pngs_to_pdf.py --margin 30 -o output.pdf

This python script is AI generated, so if there's something wrong, let me know.

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Console Script (legacy version)

For one-off use without installing the extension.

Usage

1. Open a book in Digitální Knihovna
2. Open DevTools (F12 or Cmd+Option+I) → Console tab
3. Paste the contents of console_script.js and press Enter
4. Start the scraper:

start()                  // download all pages starting from page 1
start(5)                 // start from page 5, download all remaining
start(1, 20)             // download 20 pages starting from page 1

5. To stop early:

stop()

Config

Edit the config object at the top of the script before pasting:

Option	Default	Description
startPage	1	Starting page number (also sets filename numbering)
totalPages	Infinity	How many pages to download before stopping
xhrIdleDelay	2000	ms to wait after last XHR activity before capturing
stabilityPollInterval	600	ms between canvas stability checks
stabilityRequiredMatches	3	Consecutive identical snapshots required before saving

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