C2PA Python
Python bindings for the C2PA Content Authenticity Initiative (CAI) library.
This library enables you to read and validate C2PA data in supported media files and add signed manifests to supported media files.
WARNING: This is an early prerelease version of this library. There may be bugs and unimplemented features, and the API is subject to change.
Installation
Install from PyPI by entering this command:
pip install -U c2pa-python
This is a platform wheel built with Rust that works on Windows, macOS, and most Linux distributions (using manylinux). If you need to run on another platform, see Development for information on how to build from source.
Reinstalling
If you tried unsuccessfully to install this package before the 0.40 release, then use this command to reinstall:
pip install --upgrade --force-reinstall c2pa-python
Usage
Import
Import the C2PA module as follows:
import c2pa
Read and validate C2PA data in a file
Use the read_file
function to read C2PA data from the specified file:
json_store = c2pa.read_file("path/to/media_file.jpg", "path/to/data_dir")
This function examines the specified media file for C2PA data and generates a JSON report of any data it finds. If there are validation errors, the report includes a validation_status
field. For a summary of supported media types, see Supported file formats.
A media file may contain many manifests in a manifest store. The most recent manifest is identified by the value of the active_manifest
field in the manifests map.
If the optional data_dir
is provided, the function extracts any binary resources, such as thumbnails, icons, and C2PA data into that directory. These files are referenced by the identifier fields in the manifest store report.
NOTE: For a comprehensive reference to the JSON manifest structure, see the Manifest store reference.
Add a signed manifest to a media file
Use the sign_file
function to add a signed manifest to a media file.
result = c2pa.sign_file("path/to/source.jpg",
"path/to/dest.jpg",
manifest_json,
sign_info,
data_dir)
The parameters (in order) are:
- The source (original) media file.
- The destination file that will contain a copy of the source file with the manifest data added.
manifest_json
, a JSON-formatted string containing the manifest data you want to add; see Creating a manifest JSON definition file below.sign_info
, aSignerInfo
object instance; see Generating SignerInfo below.data_dir
optionally specifies a directory path from which to load resource files referenced in the manifest JSON identifier fields; for example, thumbnails, icons, and manifest data for ingredients.
Create a SignerInfo instance
A SignerInfo
object contains information about a signature. To create an instance of SignerInfo
, first set up the signer information from the public and private key .pem
files as follows:
certs = open("path/to/public_certs.pem","rb").read()
prv_key = open("path/to/private_key.pem","rb").read()
Then create a new SignerInfo
instance using the keys as follows, specifying the signing algorithm used and optionally a time stamp authority URL:
sign_info = c2pa.SignerInfo("es256", certs, priv_key, "http://timestamp.digicert.com")
For the list of supported signing algorithms, see Creating and using an X.509 certificate.
Creating a manifest JSON definition file
The manifest JSON string defines the C2PA manifest to add to the file.
manifest_json = json.dumps({
"claim_generator": "python_test/0.1",
"assertions": [
{
"label": "c2pa.training-mining",
"data": {
"entries": {
"c2pa.ai_generative_training": { "use": "notAllowed" },
"c2pa.ai_inference": { "use": "notAllowed" },
"c2pa.ai_training": { "use": "notAllowed" },
"c2pa.data_mining": { "use": "notAllowed" }
}
}
}
]
})
Supported file formats
Extensions | MIME type |
---|---|
avi | video/msvideo , video/avi , application-msvideo |
avif | image/avif |
c2pa | application/x-c2pa-manifest-store |
dng | image/x-adobe-dng |
heic | image/heic |
heif | image/heif |
jpg , jpeg | image/jpeg |
m4a | audio/mp4 |
mp4 | video/mp4 , application/mp4 |
mov | video/quicktime |
png | image/png |
svg | image/svg+xml |
tif ,tiff | image/tiff |
wav | audio/x-wav |
webp | image/webp |
Development
It is best to set up a virtual environment for development and testing. To build from source on Linux, install curl
and rustup
then set up Python.
First update apt
then (if needed) install curl
:
apt update
apt install curl
Install Rust:
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"
Install Python, pip
, and venv
:
apt install python3
apt install pip
apt install python3.11-venv
python3 -m venv .venv
Build the wheel for your platform:
source .venv/bin/activate
pip install maturin
pip install uniffi-bindgen
python3 -m pip install build
pip install -U pytest
python3 -m build --wheel
ManyLinux build
Build using manylinux by using a Docker image as follows:
docker run -it quay.io/pypa/manylinux_2_28_aarch64 bash
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"
export PATH=/opt/python/cp312-cp312/bin:$PATH
pip install maturin
pip install venv
pip install build
pip install -U pytest
cd home
git clone https://github.com/contentauth/c2pa-python.git
cd c2pa-python
python3 -m build --wheel
auditwheel repair target/wheels/c2pa_python-0.4.0-py3-none-linux_aarch64.whl
Testing
We use PyTest for testing.
Run tests by entering this command:
source .venv/bin/activate
maturin develop
pytest
deactivate
For example:
source .venv/bin/activate
maturin develop
python3 tests/training.py
deactivate
Release notes
Version 0.4.0
This release:
- Changes the name of the import from
c2pa-python
toc2pa
. - Supports pre-built platform wheels for macOS, Windows and manylinux.
Version 0.3.0
This release includes some breaking changes to align with future APIs:
C2paSignerInfo
moves thealg
to the first parameter from the 3rd.c2pa.verify_from_file_json
is nowc2pa.read_file
.c2pa.ingredient_from_file_json
is nowc2pa.read_ingredient_file
.c2pa.add_manifest_to_file_json
is nowc2pa.sign_file
.- There are many more specific errors types now, and Error messages always start with the name of the error i.e (str(err.value).startswith("ManifestNotFound")).
- The ingredient thumbnail identifier may be jumbf uri reference if a valid thumb already exists in the active manifest.
- Extracted file paths for read_file now use a folder structure and different naming conventions.
License
This package is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
Note that some components and dependent crates are licensed under different terms; please check the license terms for each crate and component for details.
Contributions and feedback
We welcome contributions to this project. For information on contributing, providing feedback, and about ongoing work, see Contributing.