## resvg
[](https://travis-ci.org/RazrFalcon/resvg)
[](https://crates.io/crates/resvg)
[](https://docs.rs/resvg)
*resvg* is an [SVG](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics) rendering library.
## Purpose
*resvg* can be used as:
- a Rust library
- a C library (see [capi](./capi))
- a CLI application (see [tools/rendersvg](./tools/rendersvg))
to render SVG files based on a
[static](http://www.w3.org/TR/SVG11/feature#SVG-static)
[SVG Full 1.1](https://www.w3.org/TR/SVG/Overview.html) subset
(see [SVG support](#svg-support) for details).
The core idea is to make a fast, small, portable, multiple-backend SVG library
designed for edge-cases.
SVG can be rendered to a raster image or to a backend's canvas (e.g. to a QWidget via QPainter).
## Why a new library?
*resvg* is competing with [librsvg], [QtSvg]
and [Inkscape] (only as a CLI SVG-to-PNG converter).
One of the major differences from other rendering libraries is that *resvg* does a lot
of preprocessing before rendering. It converts shapes to paths, resolves attributes,
removes groups and invisible elements, fixes a lot of issues in malformed SVG files.
Then it creates a simple render tree with all elements and attributes resolved.
And only then it begins rendering. So it's very easy to implement a new rendering backend.
More details [here](https://github.com/RazrFalcon/resvg/blob/master/docs/usvg_spec.adoc).
### resvg vs librsvg
*librsvg* is the main competitor to *resvg*. And even though *librsvg* itself is being
rewritten in Rust, as *resvg*, the architecture of the library is completely different:
- *librsvg* is heavily tied to the [cairo] library
- *librsvg* is heavily tied to [GNOME], which makes it painful to distribute outside the Linux ecosystem
- *librsvg* doesn't produce an intermediate rendering tree
- *librsvg* has minimal support for edge cases, which leads to rendering errors
### resvg vs Inkscape
Inkscape is often used to convert SVG to PNG, but it's not an actual competitor to *resvg*,
since it's still a complete vector editor, not a tiny library.
Also, it's very slow. But it has the best SVG support amongst others.
### resvg vs QtSvg
Without a doubt, [QtSvg] is heavily used in [Qt] applications.
But [QtSvg] itself is very limited. It officially supports only a tiny portion
of the SVG Tiny 1.2 subset. In simple terms – it correctly renders only primitive SVG images.
Also, it's [deprecated](https://wiki.qt.io/Qt_Modules_Maturity_Level).
## SVG support
*resvg* is aiming to support only the [static](http://www.w3.org/TR/SVG11/feature#SVG-static)
SVG subset; e.g. no `a`, `script`, `view` or `cursor` elements, no events and no animations.
A list of unsupported features can be found [here](docs/unsupported.md).
[SVG Tiny 1.2](https://www.w3.org/TR/SVGTiny12/) and [SVG 2.0](https://www.w3.org/TR/SVG2/)
are not supported and not planned.
Results of the static subset of the [SVG test suite](https://www.w3.org/Graphics/SVG/Test/20110816/):
Results of the [resvg test suite](https://github.com/RazrFalcon/resvg-test-suite):
You can find a complete table of supported features
[here](https://razrfalcon.github.io/resvg-test-suite/svg-support-table.html).
It also includes alternative libraries.
## Performance
Note that all tested applications have a different SVG support, which impacts the performance.
Also, we do not test against Chrome, Firefox, Inkscape and Batik because they have a huge startup time.
- Elementary Icon Theme contains 3417 files.
- Qt backend is slow because `QRasterPaintEngine` is slow.
- The Oxygen icon theme contains 4947 files.
- All images were converted from `.svgz` to `.svg` beforehand.
- `resvg` is slower than `librsvg` because the Oxygen icon theme uses Gaussian blur heavily, which is expensive.
And `librsvg` uses box blur optimization and multithreading, while `resvg` always uses a single-threaded IIR blur (at least for now).
- QtSvg doesn't support `filter`, `clipPath`, `mask` and `pattern` that are heavily used in the Oxygen icon theme.
So it's actually very slow.
## Project structure
- `resvg` – rendering backends implementation
- [`usvg`](./usvg) – an SVG simplification tool
- [`svgdom`](https://github.com/RazrFalcon/svgdom) – a DOM-like SVG tree
- [`roxmltree`](https://github.com/RazrFalcon/roxmltree) – a DOM-like XML tree
- [`xmlparser`](https://github.com/RazrFalcon/xmlparser) – an XML parser
- [`svgtypes`](https://github.com/RazrFalcon/svgtypes) – SVG types parser and writer
- [`rctree`](https://github.com/RazrFalcon/rctree) – a DOM-like tree
- [`resvg-qt`](./resvg-qt) – minimal bindings to [Qt]
All other dependencies aren't written by me for this project.
## Directory structure
- `capi` – C/FFI interface for *resvg*
- `docs` – basic documentation
- `examples` – usage examples for *resvg* as a library
- `resvg-qt` – minimal bindings to Qt used by *resvg*
- `src` – source code
- `testing-tools` – scripts used for testing
- `tools` – useful tools
- `usvg` – an SVG simplification library used by *resvg*
## Safety
- The library must not panic. Any panic should be considered a critical bug and should be reported.
There are only a few methods that can produce a panic.
- The core library structure (see above) does not use any `unsafe`,
but since all backends are implemented via FFI, we are stuck with `unsafe` anyway.
Also, `usvg` uses unsafe for fonts memory mapping.
## License
*resvg* is licensed under the [MPLv2.0](https://www.mozilla.org/en-US/MPL/).
[Inkscape]: https://www.inkscape.org
[librsvg]: https://wiki.gnome.org/action/show/Projects/LibRsvg
[QtSvg]: https://doc.qt.io/qt-5/qtsvg-index.html
[cairo]: https://www.cairographics.org/
[Qt]: https://www.qt.io/
[Skia]: https://skia.org/
[GNOME]: https://www.gnome.org/