GAP decoder

This project aims at making it possible to download images from google arts and culture (formerly Google Art Project).

How to use

Note : If you are not comfortable with installing a scripting language on your computer, you can use instead of gapdecoder:

• dezoomify, which can be used online without downloading anything to your computer, but limits the maximum size of downloaded images.
• dezoomify-rs, which comes as ready-to-use executable.

First, install python 3 on your system, and install the dependencies:

python3 -m pip install -r requirements.txt 

Then, run the code

python3 tile_fetch.py --zoom 4 "https://artsandculture.google.com/asset/the-water-carrier-la-aguadora/UwE2fGsMlWHuMg"

You can of course change the zoom level and the URL. If you omit the zoom level, the script will display the list of available levels.

Run with the '-h' flag for a list of available commands.

Technical details

This project required reverse-engineering google's code to find the protection measures in place and circumvent them. Here is what was found.

Tile URLs

The tile URLs are signed using HMAC. See the details

Tile images

The tile images are encoded using AES 128 CBC. See the details