Viewer

The Viewer provides real-time image/video display with keyboard interaction and video recording capabilities.

Window Management

Method	Description
is_window_exist_and_closed()	Check if user closed window
wait_key(ms)	Wait for key (timeout in ms)
is_open()	Check if window is open

Always check is_window_exist_and_closed() in your loop.

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Key Handling

Common Keys

• ESC — Exit
• Space — Pause/Resume
• S — Save screenshot

Example

if let Some(key) = viewer.wait_key(30) {
    match key {
        Key::Escape => break,
        Key::S => {
            images[0].save("screenshot.png")?;
        }
        _ => {}
    }
}

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Video Recording

Requires video feature

Add to Cargo.toml: features = ["video"]

Example

let mut viewer = Viewer::default()
    .with_record_output("output.mp4")?;

for (images, _) in dl {
    viewer.imshow(&images[0])?;
    viewer.write_video_frame(&images[0])?;

    if viewer.is_window_exist_and_closed() {
        break;
    }
}

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Example

imshow

use clap::Parser;
use usls::{DataLoader, Source, Viewer};

#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args {
    /// Data source.
    #[arg(long, required = true)]
    source: Source,

    /// Save frames to video.
    #[arg(long, default_value = "false")]
    save: bool,

    /// Window scale.
    #[arg(long, default_value = "0.8")]
    window_scale: f32,

    /// Delay in milliseconds between frames.
    #[arg(long, default_value = "1")]
    delay: u64,

    /// Num of frames to skip.
    #[arg(long, default_value = "0")]
    nfv_skip: u64,
}

fn main() -> anyhow::Result<()> {
    let args = Args::parse();
    let dl = DataLoader::new(args.source)?
        .with_nfv_skip(args.nfv_skip)
        .stream()?;
    let mut viewer = Viewer::default().with_window_scale(args.window_scale);

    for images in &dl {
        // Check if the window is closed and exit if so.
        if viewer.is_window_exist_and_closed() {
            break;
        }

        // Display the current image.
        viewer.imshow(&images[0])?;

        // Wait for a key press or timeout, and exit on Escape.
        if let Some(key) = viewer.wait_key(args.delay) {
            if key == usls::Key::Escape {
                break;
            }
        }

        // Save the current frame to video if requested.
        // Note: For multiple videos, frames will be saved to separate files.
        if args.save {
            viewer.write_video_frame(&images[0])?;
        }
    }

    Ok(())
}

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