Glycin

Glycin allows to decode images into gdk::Textures and to extract image metadata. The decoding happens in sandboxed modular image loaders.

• glycin – The image library
• glycin-utils – Utilities to write loaders for glycin
• loaders – Glycin loaders for several formats

Example

```rust let file = gio::File::for_path("image.jpg"); let image = ImageRequest::new(file).request().await?;

let height = image.info().height; let texture = image.next_frame().await?; ```

Image loader configuration

Loader configurations are read from XDG_DATA_DIRS and XDG_DATA_HOME. The location is typically of the from

<data-dir>/share/glycin/<compat-version>+/conf.d/<loader-name>.conf

so for example

<data-dir>/share/glycin/0+/conf.d/glyicn-image-rs.conf

The configs are glib KeyFiles of the the form

ini [loader:image/png] Exec = /usr/libexec/glycin/0+/glycin-image-rs

Where the part behind loader is a mime-type and the value of Exec can be any executable path.

Existing compatibility versions

Not every new major version of the library has to break compatibility with the loaders. The following compatibility versions currently exist

| compat-version | |----------------| | 0+ |

Supported image formats

The following features are supported by the glycin loaders provided in the loaders directory.

| Format | Decoder | ICC | CICP | EXIF | XMP | Animation | Library | |-----------|----------|-----|------|------|-----|-----------|----------------------------| | AVIF | heif | ✔ | ✔ | ✔ | ✘ | ✘ | libheif-rs + libheif (C++) | | BMP | image-rs | ✘ | — | — | — | — | image-rs | | DDS | image-rs | — | — | — | — | — | image-rs | | farbfeld | no mime | — | — | — | — | — | image-rs | | QOI | image-rs | — | — | — | — | — | image-rs | | GIF | image-rs | ✘ * | — | — | ✘ | ✔ | image-rs | | HEIC | heif | ✔ | ✔ | ✔ | ✘ | ✘ | libheif-rs + libheif (C++) | | ICO | image-rs | — | — | — | — | — | image-rs | | JPEG | image-rs | ✔ | — | ✔ | ✘ | — | image-rs | | JPEG 2000 | TODO | ✘ | — | ✘ | ？ | ✘ | jpeg2k? + openjpeg (C) | | JPEG XL | jxl | ✔ | ✘ | ✘ | ✘ | ✘ | jxl-oxide | | OpenEXR | image-rs | — | — | — | — | — | image-rs | | PNG | image-rs | ✔ | ✘ | ✔ | ✘ | ✔ | image-rs | | PNM | image-rs | — | — | — | — | — | image-rs | | SVG | image-rs | ✘ | — | — | ✘ * | — | librsvg + gdk-pixbuf | | TGA | image-rs | — | — | — | — | — | image-rs | | TIFF | image-rs | ✔ | — | ✔ | ✘ | — | image-rs | | WEBP | image-rs | ✔ | — | ✔ | ✘ | ✔ | image-rs + libwebp (C) |

| Symbol | Meaning | |--------|------------------------------------------------| | ✔ | Supported | | ✘ | Supported by format but not implemented yet | | — | Not available for this format | | ？ | Unclear if supported by format, needs research | | * | Unclear if used in practice, needs research |

Building and Testing

• The -Dloaders option allows to only build certain loaders.
• The -Dtest_skip_ext option allows to skip certain image filename extensions during tests. The -Dtest_skip_ext=heic might be needed if x265 is not available.
• Running integration tests requires the glycin loaders to be installed. By default this is done by meson test automatically. This behavior can be changed by setting -Dtest_skip_install=true.

License

SPDX-License-Identifier: MPL-2.0 OR LGPL-2.1-or-later