Function run_resolution_test

rustcv-camera/examples/resolution_bench.rs:85–139

Run a single resolution test with live preview window. 运行单次分辨率测试，带实时预览窗口。 Captures frames for ~5 seconds (or until ESC), returns average FPS. 采集约 5 秒的帧（或按 ESC 退出），返回平均 FPS。

(
    test: &ResolutionTest,
)

/// Captures frames for ~5 seconds (or until ESC), returns average FPS.
/// 采集约 5 秒的帧（或按 ESC 退出），返回平均 FPS。
fn run_resolution_test(
    test: &ResolutionTest,
) -> std::result::Result<(f64, String), Box<dyn std::error::Error>> {
    let config = CameraConfig::new()
        .resolution(test.width, test.height)
        .fps(30);

    let mut cap = VideoCapture::open_with(0, config)?;
    let actual_w = cap.width() as usize;
    let actual_h = cap.height() as usize;
    let format = cap.camera().pixel_format().to_string();

    println!(
        "  Opened: {}x{} {} (requested {}x{})",
        actual_w, actual_h, format, test.width, test.height
    );

    // Create window sized to actual resolution.
    // 创建与实际分辨率匹配的窗口。
    let title = format!("rustcv-camera {} ({}x{})", test.label, actual_w, actual_h);
    let mut window = Window::new(&title, actual_w, actual_h, WindowOptions::default())?;

    let mut frame = Mat::new();
    let mut display_buf: Vec<u32> = vec![0; actual_w * actual_h];

    let start = Instant::now();
    let mut fps_timer = Instant::now();
    let mut fps_count: u32 = 0;
    let mut fps_display: f64 = 0.0;
    let mut total_frames: u64 = 0;

    // Run for ~5 seconds or until ESC.
    // 运行约 5 秒或按 ESC 退出。
    while window.is_open() && !window.is_key_down(Key::Escape) && start.elapsed().as_secs() < 5 {
        if !cap.read(&mut frame)? {
            break;
        }

        bgr_to_u32(frame.data(), &mut display_buf);
        draw_fps_overlay(&mut display_buf, actual_w, fps_display, test.label);
        window.update_with_buffer(&display_buf, actual_w, actual_h)?;

        total_frames += 1;
        fps_count += 1;
        let elapsed = fps_timer.elapsed().as_secs_f64();
        if elapsed >= 1.0 {
            fps_display = fps_count as f64 / elapsed;
            fps_count = 0;
            fps_timer = Instant::now();
        }
    }

    let avg_fps = total_frames as f64 / start.elapsed().as_secs_f64();
    Ok((avg_fps, format))
}

/// Convert BGR byte slice to u32 display buffer (0x00RRGGBB).
/// 将 BGR 字节切片转换为 u32 显示缓冲区（0x00RRGGBB）。