Ratatui-image

Showcase:

Link to screenshot test suite with array of terminals (xterm, foot, kitty, wezterm, ghostty, rio, mlterm...)

Image widgets with multiple graphics protocol backends for ratatui

Unify terminal image rendering across Sixels, Kitty, and iTerm2 protocols.

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. Query the terminal with some control sequences for either the font-size directly, or the window-size in pixels and derive the font-size together with row/column count.

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. Since we have the font-size in pixels, we can precisely map the characters/cells/rows-columns that will be covered by the image and skip drawing over the image.

Quick start

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::halfblocks();

    // Load an image with the image crate.
    let dyn_img = image::ImageReader::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))?;
    // It is recommended to handle the encoding result
    app.image.last_encoding_result().unwrap()?;
    Ok(())
}

fn ui(f: &mut Frame<'_>, app: &mut App) {
    // The image widget.
    let image = StatefulImage::default();
    // Render with the protocol state.
    f.render_stateful_widget(image, f.area(), &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 has a fixed size in rows/columns. If the image pixel size exceeds the pixel area of the rows/columns, the image is scaled down proportionally to "fit" once. If the actual rendering area is smaller than the initial rows/columns, it is simply not rendered at all. The big upside is that this widget 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, so this factor is also important when chosing.
• The [StatefulImage] widget adapts to its render area at render-time. It can be set to fit, crop, or scale to the available render area. This means the widget must be stateful, i.e. use render_stateful_widget which takes a mutable state parameter. The resizing and encoding is blocking, and since it happens at render-time it is a good idea to offload that to another thread or async task, if the UI must be responsive (see examples/thread.rs and examples/tokio.rs).

Examples

• examples/demo.rs is a fully fledged demo.
• examples/thread.rs shows how to offload resize and encoding to another thread, to avoid blocking the UI thread.
• examples/tokio.rs same as thread.rs but with tokio.

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

Features

Backend

• crossterm (default) if this matches your ratatui backend (most likely).
• termion if this matches your ratatui backend.
• termwiz is available, but not working correctly with ratatui-image.

Chafa library

• chafa-dyn (default) to use the amazing chafa library for rendering without image protocols. Dynamically link against libchafa.so at compile time. Requires libchafa to be available at runtime in the same way.
• chafa-static to statically link against libchafa.a at compile time. The library is embedded in the binary.
• If you absolutely don't want to deal with libchafa, then you should use --no-default-features --features image-defaults,crossterm or a variation thereof.

Note: The chafa features are mutually exclusive - only enable one at a time.

Others

• 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/.

• serde for #[derive]s on [picker::ProtocolType] for convenience, because it might be useful to save it in some user configuration.

• tokio whether to use tokio's UnboundedSender in ThreadProtocol.

Compatibility matrix

Compatibility and QA:

iTerm2 | iTerm2 | ✔️ | - | Reference for the iTerm2 protocol. Mac only. Rio | iTerm2 | ✔️ | ✔️ | Also supports Sixel but has glitches. mlterm | Sixel | ✔️ | ✔️ | Quite slow but no glitches. Black Box | Sixel | ✔️ | - | Confirmed only with the flatpak version, most distro packages don't enable Sixel support. Bobcat | iTerm2 | ✔️ | - | Works on all versions and builds. Falls back to Sixel if TERM_PROGRAM variable is not set. Alacritty | Sixel | ❌ | - | There is a sixel fork, but it's probably never getting merged, and does not clear graphics. Konsole | Sixel | ❌ | - | Not really fixed in 24.12 Contour | Sixel | ❌ | ❌ | Does not clear graphics. ctx | Sixel | ❌ | ❌ | Buggy. Warp | iTerm2 | ❌ | - | iTerm2 does not clear, Kitty unicode-placeholders part not implemented.

"QA" means that there is a flake VM test that runs the demo and takes a screenshot, posted as PR comment. - means it's not possible or applicable to add a screenshot-test.

Link to latest screenshot of the test-suite on master

Halfblocks should work in all terminals, even if the font size could not be detected, with a 4:8 pixel ratio.

Known issues

Projects that use ratatui-image

• mdfried A markdown viewer that renders headers bigger (as images), and regular images too.
• iamb A matrix client with vim keybindings.
• joshuto A terminal file manager that can preview images.
• Aerostream A Bluesky client using EventStream.
• Eilmeldung RSS reader

Comparison

• 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 Not a library but a terminal file manager that implementes many graphics protocols and lets you preview images in the filesystem.
• Überzug++ 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.

Contributing

PRs and issues/discussions welcome!

There are some specific rules for a PR to be reviewed at all, please see CONTRIBUTING.md for reference.

License: MIT