# Ratatui-image

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[Docs]: https://docs.rs/ratatui-image/latest/ratatui_image/index.html

### Showcase:

![Recording](./assets/Recording.gif)

## Image widgets with multiple graphics protocol backends for [ratatui]

[ratatui] is an immediate-mode TUI library.
ratatui-image tackles 3 general problems when rendering images with an immediate-mode TUI:

**Query the terminal for available graphics protocols**

Some terminals may implement one or more graphics protocols, such as Sixels, or the iTerm2 or
Kitty graphics protocols. Guess by env vars. If that fails, query the terminal with some
control sequences.
Fallback to "halfblocks" which uses some unicode half-block characters with fore- and
background colors.

**Query the terminal for the font-size in pixels.**

If there is an actual graphics protocol available, it is necessary to know the font-size to
be able to map the image pixels to character cell area. The image can be resized, fit, or
cropped to an area. Query the terminal for the window and columns/rows sizes, and derive the
font-size.

**Render the image by the means of the guessed protocol.**

Some protocols, like Sixels, are essentially "immediate-mode", but we still need to avoid the
TUI from overwriting the image area, even with blank characters.
Other protocols, like Kitty, are essentially stateful, but at least provide a way to re-render
an image that has been loaded, at a different or same position.

## Quick start
```rust
use ratatui::{backend::TestBackend, Terminal, Frame};
use ratatui_image::{picker::Picker, StatefulImage, protocol::StatefulProtocol};

struct App {
    // We need to hold the render state.
    image: StatefulProtocol,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let backend = TestBackend::new(80, 30);
    let mut terminal = Terminal::new(backend)?;

    // Should use Picker::from_query_stdio() to get the font size and protocol,
    // but we can't put that here because that would break doctests!
    let mut picker = Picker::from_fontsize((8, 12));

    // Load an image with the image crate.
    let dyn_img = image::io::Reader::open("./assets/Ada.png")?.decode()?;

    // Create the Protocol which will be used by the widget.
    let image = picker.new_resize_protocol(dyn_img);

    let mut app = App { image };

    // This would be your typical `loop {` in a real app:
    terminal.draw(|f| ui(f, &mut app))?;

    Ok(())
}

fn ui(f: &mut Frame<'_>, app: &mut App) {
    // The image widget.
    let image = StatefulImage::new(None);
    // Render with the protocol state.
    f.render_stateful_widget(image, f.size(), &mut app.image);
}
```

The [picker::Picker] helper is there to do all this font-size and graphics-protocol guessing,
and also to map character-cell-size to pixel size so that we can e.g. "fit" an image inside
a desired columns+rows bound, and so on.

## Widget choice
* The [Image] widget does not adapt to rendering area (except not drawing at all if space
  is insufficient), may be a bit more bug prone (overdrawing or artifacts), and is not friendly
  with some of the protocols (e.g. the Kitty graphics protocol, which is stateful). Its big
  upside is that it is _stateless_ (in terms of ratatui, i.e. immediate-mode), and thus can never
  block the rendering thread/task. A lot of ratatui apps only use stateless widgets.
* The [StatefulImage] widget adapts to its render area, is more robust against overdraw bugs and
  artifacts, and plays nicer with some of the graphics protocols.
  The resizing and encoding is blocking by default, but it is possible to offload this to another
  thread or async task (see `examples/async.rs`). It must be rendered with
  [`render_stateful_widget`] (i.e. with some mutable state).

## Examples

* `examples/demo.rs` is a fully fledged demo.
* `examples/async.rs` shows how to offload resize and encoding to another thread, to avoid
  blocking the UI thread.

The lib also includes a binary that renders an image file, but it is focused on testing.

## Features
* `crossterm` or `termion` should match your ratatui backend. `termwiz` is available, but not
  working correctly with ratatu-image.
* `serde` for `#[derive]`s on [picker::ProtocolType] for convenience, because it might be
  useful to save it in some user configuration.
* `image-defaults` (default) just enables `image/defaults` (`image` has `default-features =
false`). To only support a selection of image formats and cut down dependencies, disable this
  feature, add `image` to your crate, and enable its features/formats as desired. See
  https://doc.rust-lang.org/cargo/reference/features.html#feature-unification.

[ratatui]: https://github.com/ratatui-org/ratatui
[sixel]: https://en.wikipedia.org/wiki/Sixel
[`render_stateful_widget`]: https://docs.rs/ratatui/latest/ratatui/terminal/struct.Frame.html#method.render_stateful_widget

### Compatibility matrix

Compatibility and QA:

Terminal  | Protocol | Fixed | Resize | Notes
----------|----------|-------|--------|-------
Xterm     | `Sixel`  | ✔️     | ✔️      | Run with `-ti 340` to make sure sixel support is enabled.
Foot      | `Sixel`  | ✔️     | ✔️      | Wayland.
kitty     | `Kitty`  | ✔️     | ✔️      |
Wezterm   | `iTerm2` | ✔️     | ✔️      | Also would support `Sixel` and `Kitty`, but only `iTerm2` actually works bug-free.
Alacritty | `Sixel`  | ❌    | ❌     | [There is a sixel fork](https://github.com/microo8/alacritty-sixel), but it's stale and does not clear graphics.
iTerm2    | `iTerm2` | ❔    | ❔     | Untested (needs apple hardware), however should be the same as WezTerm.
konsole   | `Sixel`  | ❌    | ❌     | [Wontfix: does not clear graphics](https://bugs.kde.org/show_bug.cgi?id=456354), other artifacts.
Contour   | `Sixel`  | ❌    | ❌     | Does not clear graphics.
ctx       | `Sixel`  | ❌    | ❌     | Buggy.
Blackbox  | `Sixel`  | ❔    | ❔     | Untested.

Here, "Fixed" means the `Image` widget, and "Resize" is the `StatefulWidget`.

A basic [screenshot test](./assets/screenshot_xterm.png) is run with xterm on Xvfb in the CI (or `cargo make screenshot-xvfb && cargo make screenshot-diff`).

Halfblocks should work in all terminals.

### Projects that use ratatui-image

* [iamb](https://github.com/ulyssa/iamb)
  A matrix client with vim keybindings.
* [joshuto](https://github.com/kamiyaa/joshuto)
  A terminal file manager that can preview images.
* [Aerostream](https://github.com/shigepon7/aerostream)
  A Bluesky client using EventStream.

### Comparison

* [viuer](https://crates.io/crates/viuer)
  Renders graphics in different terminals/protocols, but "dumps" the image, making it difficult to
  work for TUI programs.
  The terminal protocol guessing code has been adapted to rustix, thus the author of viuer is
  included in the copyright notice.
* [yazi](https://github.com/sxyazi/yazi)
  Not a library but a terminal file manager that implementes many graphics protocols and lets you
  preview images in the filesystem.
* [Überzug++](https://github.com/jstkdng/ueberzugpp)
  CLI utility that draws images on terminals by using X11/wayland child windows, sixels, kitty,
  and/or iterm2 protocols (any means necessary). There exists several wrapper or bindings crates.
  More battle-tested but essentially stateful, which makes it hard to use with immediate-mode.

License: MIT