# ImageSharp build license

ChaptarrNG uses `SixLabors.ImageSharp` to resize book, author, and narrator
cover images in `src/NzbDrone.Core/MediaCover/ImageResizer.cs`. The package is a
direct dependency of `src/NzbDrone.Core/Chaptarr.Core.csproj`.

## Why a license is required

Starting with ImageSharp 4.0, Six Labors validates licenses at build time for
projects that directly reference ImageSharp. ChaptarrNG uses ImageSharp 4.1.3,
so source builds must provide a valid Six Labors license. This is a build-time
dependency requirement; the application does not read the build key at
runtime. Official ChaptarrNG images contain a build made with a valid license,
so running one does not require configuring a build key. The Six Labors Split
License still governs use of ImageSharp; review its current terms and confirm
that your use qualifies.

The Six Labors license is separate from ChaptarrNG's GPL license. When
requesting an open-source or source-available community license, provide the
case-sensitive assembly name for every project that directly references
ImageSharp. Include a test project only if it also references ImageSharp
directly. Use the project's `AssemblyName`, or its project filename without
`.csproj` when `AssemblyName` is unset; do not include `.dll` or `.csproj`.
The direct reference in this repository is in
`src/NzbDrone.Core/Chaptarr.Core.csproj`.

## Obtain a license

Apply through the [Six Labors licensing portal](https://licensing.sixlabors.com/).
Review the current [ImageSharp license terms and options](https://docs.sixlabors.com/articles/imagesharp/index.html#license),
select the option that matches your use, and enter the required assembly names.
Six Labors sends the issued license as `sixlabors.lic`. Use the complete file
contents when configuring builds; do not extract only its `Key` field. Since
this repository does not publish its license file or share the Actions secret
with fork pull requests, contributors building from source need to provide an
eligible license for their own build.

ChaptarrNG does not commit the license file or key. Keep the file outside the
repository, and keep `.env.sixlabors` private. The repository ignores that env
file and the Docker build context excludes license files.

## Local source builds

Create the ignored repository-root `.env.sixlabors` file with a private editor
or secret manager. It should contain one shell-quoted assignment with the full
contents of `sixlabors.lic`; do not put the actual value in a shell command:

```dotenv
SIXLABORS_LICENSE_KEY='<complete contents of sixlabors.lic>'
```

```sh
chmod 600 .env.sixlabors
set -a
. ./.env.sixlabors
set +a
dotnet restore src/Chaptarr.NoTests.sln
dotnet build src/Chaptarr.NoTests.sln --configuration Release
unset SIXLABORS_LICENSE_KEY
```

`src/Directory.Build.props` passes `SIXLABORS_LICENSE_KEY` to the ImageSharp
build target. If you are running the validation engine, follow its instructions
to build with the license and clear the variable before starting the engine.

## GitHub Actions builds

In the repository's **Settings → Secrets and variables → Actions**, add a
repository secret named `SIXLABORS_LICENSE_KEY` containing the complete
`sixlabors.lic` file contents. The build and image-publish workflows pass it to
the build only. GitHub does not provide repository secrets to workflows started
from fork pull requests, so those workflows cannot perform the licensed build.

## Local Docker builds

Source `.env.sixlabors` in the shell, then pass the environment variable as a
BuildKit secret:

```sh
set -a
. ./.env.sixlabors
set +a
docker buildx build --secret id=SIXLABORS_LICENSE_KEY,env=SIXLABORS_LICENSE_KEY -f Dockerfile.cross .
unset SIXLABORS_LICENSE_KEY
```

The Dockerfile mounts the secret only for the restore/publish build step. It is
not copied into the build context, image layers, runtime environment, or image
metadata. Do not add the key to a Docker `ARG`, `ENV`, or runtime configuration.

## References

- [Six Labors ImageSharp license and build setup](https://docs.sixlabors.com/articles/imagesharp/index.html#license)
- [Six Labors licensing portal](https://licensing.sixlabors.com/)
- [ChaptarrNG validation-engine build instructions](validation-engine.md#local-use)