# tinyvg-rs
This is a Rust implementation of the [TinyVG](https://tinyvg.tech) image format.
It provides an executable that renders PNG images from TinyVG input files, and a
library that can render PNG images or any format supported by
`piet::RenderContext`.
# Dependencies
All dependencies but one are managed by cargo. This program/library does depend
on cairo for rendering PNGs. You should be able to install cairo using your OS
package manager.
# Executable
## Installation
```
$ cargo install tinyvg
```
## Usage
```
tinyvg 0.1.0
TinyVG to PNG renderer
USAGE:
tinyvg [OPTIONS] <input>
FLAGS:
-h, --help Prints help information
-V, --version Prints version information
OPTIONS:
-o <output> Optional output path. If not specified, uses the input path with a `.png` suffix
ARGS:
<input> Input path to TinyVG binary file
```
# Library Usage
```rust
use tinyvg::Decoder;
use std::fs::File;
fn main() -> eyre::Result<()> {
// Build a decoder from a `std::io::Read`. Here a file is used, but any type
// that implements `Read` can be used.
let decoder = Decoder::new(File::open("data/shield.tvg")?);
let image = decoder.decode()?;
let mut out = File::create("out.png")?;
// Render the image to a PNG file. Here a file is used, but any type
// that implements `std::io::Write` can be used.
image.render_png(&mut out)?;
Ok(())
}
```
## Features
- `render-png` (default) - enables the ability to render TinyVG images into PNG files.
Disabling this removes the cairo dependency. This can be useful if you're already using
piet with another backend.
# Development
## Testing
There are some doctests which validate that certain files can be decoded and
rendered without errors, but there currently isn't much in the way of automated
testing. I wasn't sure how to effectively write equality tests without writing a
massive amount of code. There is an example program which will crawl the `data`
directory and render all `.tvg` files into `.png` files with the same names.
This can be used to validate rendering behavior for example images.
```
$ cargo run --example render-all
path render time
data/app_icon.tvg 78.94075ms
data/chart.tvg 14.194083ms
data/comic.tvg 23.534791ms
data/everything.tvg 21.251875ms
data/flowchart.tvg 5.075ms
data/shield.tvg 597.916µs
data/tiger.tvg 35.942166ms
$ open data/tiger.png
```
There is also a criterion benchmarking suite which tests decoding and rendering.
```
$ cargo bench
TinyVG/decode/tiger.tvg time: [135.98 us 136.65 us 137.34 us]
TinyVG/render/tiger.tvg time: [27.541 ms 27.629 ms 27.744 ms]
```