vello_cpu 0.0.4

A CPU-based renderer for Vello, optimized for SIMD and multithreaded execution.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

<div align="center">

# Vello CPU

**CPU-based renderer**

[![Latest published version.](https://img.shields.io/crates/v/vello_cpu.svg)](https://crates.io/crates/vello_cpu)
[![Documentation build status.](https://img.shields.io/docsrs/vello_cpu.svg)](https://docs.rs/vello_cpu)
[![Apache 2.0 or MIT license.](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](#license)
\
[![Linebender Zulip chat.](https://img.shields.io/badge/Linebender-%23vello-blue?logo=Zulip)](https://xi.zulipchat.com/#narrow/channel/197075-vello)
[![GitHub Actions CI status.](https://img.shields.io/github/actions/workflow/status/linebender/vello/ci.yml?logo=github&label=CI)](https://github.com/linebender/vello/actions)
[![Dependency staleness status.](https://deps.rs/crate/vello_cpu/latest/status.svg)](https://deps.rs/crate/vello_cpu)

</div>

<!-- We use cargo-rdme to update the README with the contents of lib.rs.
To edit the following section, update it in lib.rs, then run:
cargo rdme --workspace-project=vello_cpu --heading-base-level=0
Full documentation at https://github.com/orium/cargo-rdme -->

<!-- Intra-doc links used in lib.rs should be evaluated here.
See https://linebender.org/blog/doc-include/ for related discussion. -->

[`RenderContext`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html
[RenderContext::set_paint]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.set_paint
[RenderContext::fill_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.fill_path
[RenderContext::stroke_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.stroke_path
[RenderContext::glyph_run]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.glyph_run
[`RenderContext::render_to_pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.render_to_pixmap
[`Pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.Pixmap.html
[libm]: https://crates.io/crates/libm

<!-- cargo-rdme start -->

Vello CPU is a 2D graphics rendering engine written in Rust, for devices with no or underpowered GPUs.

It is currently available as an alpha.
See the [Caveats](#caveats) section for things you need to be aware of.

We also develop [Vello](https://crates.io/crates/vello), which makes use of the GPU for 2D rendering and has higher performance than Vello CPU.
Vello CPU is being developed as part of work to address shortcomings in Vello.

## Usage

To use Vello CPU, you need to:

- Create a [`RenderContext`][], a 2D drawing context for a fixed-size target area.
- For each object in your scene:
  - Set how the object will be painted, using [`set_paint`][RenderContext::set_paint].
  - Set the shape to be drawn for that object, using methods like [`fill_path`][RenderContext::fill_path],
    [`stroke_path`][RenderContext::stroke_path], or [`glyph_run`][RenderContext::glyph_run].
- Render it to an image using [`RenderContext::render_to_pixmap`][].

```rust
use vello_cpu::{RenderContext, Pixmap, RenderMode};
use vello_cpu::{color::{palette::css, PremulRgba8}, kurbo::Rect};
let width = 10;
let height = 5;
let mut context = RenderContext::new(width, height);
context.set_paint(css::MAGENTA);
context.fill_rect(&Rect::from_points((3., 1.), (7., 4.)));

let mut target = Pixmap::new(width, height);
// This is only necessary if you activated the `multithreading` feature.
context.flush();
context.render_to_pixmap(&mut target);

let expected_render = b"\
    0000000000\
    0001111000\
    0001111000\
    0001111000\
    0000000000";
let magenta = css::MAGENTA.premultiply().to_rgba8();
let transparent = PremulRgba8 {r: 0, g: 0, b: 0, a: 0};
let mut result = Vec::new();
for pixel in target.data() {
    if *pixel == magenta {
        result.push(b'1');
    } else if *pixel == transparent {
        result.push(b'0');
    } else {
         panic!("Got unexpected pixel value {pixel:?}");
    }
}
assert_eq!(&result, expected_render);
```

## Features

- `std` (enabled by default): Get floating point functions from the standard library
  (likely using your target's libc).
- `libm`: Use floating point implementations from `libm`.
- `png`(enabled by default): Allow loading [`Pixmap`]s from PNG images.
  Also required for rendering glyphs with an embedded PNG.
- `multithreading`: Enable multi-threaded rendering.

At least one of `std` and `libm` is required; `std` overrides `libm`.

## Caveats

Vello CPU is an alpha for several reasons, including the following.

### API stability

This API has been developed for an initial version, and has no stability guarantees.
Whilst we are in the `0.0.x` release series, any release is likely to breaking.
We have known plans to change the API around how image resources are used.

### Documentation

We have not yet put any work into documentation.

### Performance

We do not perform several important optimisations, such as the use of multithreading and SIMD.
Additionally, some algorithms we use aren't final, and will be replaced with higher-performance variants.

## Implementation

TODO: Point to documentation of sparse strips pattern.

<!-- cargo-rdme end -->

## Minimum supported Rust Version (MSRV)

This version of Vello CPU has been verified to compile with **Rust 1.86** and later.

Future versions of Vello CPU might increase the Rust version requirement.
It will not be treated as a breaking change and as such can even happen with small patch releases.

<details>
<summary>Click here if compiling fails.</summary>

As time has passed, some of Vello CPU's dependencies could have released versions with a higher Rust requirement.
If you encounter a compilation issue due to a dependency and don't want to upgrade your Rust toolchain, then you could downgrade the dependency.

```sh
# Use the problematic dependency's name and version
cargo update -p package_name --precise 0.1.1
```

</details>

## Community

Discussion of Vello CPU development happens in the [Linebender Zulip](https://xi.zulipchat.com/), specifically the [#vello channel](https://xi.zulipchat.com/#narrow/channel/197075-vello).
All public content can be read without logging in.

Contributions are welcome by pull request.
The [Rust code of conduct] applies.

## License

Licensed under either of

- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)

at your option.

[Rust code of conduct]: https://www.rust-lang.org/policies/code-of-conduct