Function main

rustcv-camera/examples/camera_demo.rs:11–66

()

use rustcv_camera::{Mat, VideoCapture};

fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
    println!("=== rustcv-camera: Camera Preview ===");

    let mut cap = VideoCapture::open(0)?;
    let width = cap.width() as usize;
    let height = cap.height() as usize;
    println!("Camera opened: {}x{}", width, height);

    // Create display window.
    // 创建显示窗口。
    let mut window = Window::new("rustcv-camera", width, height, WindowOptions::default())?;

    // Pre-allocate buffers — reused every frame, zero allocation in the hot loop.
    // 预分配缓冲区 —— 每帧复用，热循环中零分配。
    let mut frame = Mat::new();
    let mut display_buf: Vec<u32> = vec![0; width * height];

    // FPS calculation.
    // FPS 计算。
    let mut fps_timer = Instant::now();
    let mut fps_count: u32 = 0;
    let mut fps_display: f64 = 0.0;

    println!("Press ESC to exit.");

    while window.is_open() && !window.is_key_down(Key::Escape) {
        if !cap.read(&mut frame)? {
            break;
        }

        // Convert BGR Mat → u32 display buffer (0x00RRGGBB for minifb).
        // 将 BGR Mat 转换为 u32 显示缓冲区（minifb 使用 0x00RRGGBB 格式）。
        bgr_to_u32(frame.data(), &mut display_buf);

        // Draw FPS text as simple digit overlay in top-left corner.
        // 在左上角绘制简单的 FPS 数字叠加。
        draw_fps_overlay(&mut display_buf, width, fps_display);

        // Update window.
        // 更新窗口。
        window.update_with_buffer(&display_buf, width, height)?;

        // Update FPS counter every second.
        // 每秒更新一次 FPS 计数。
        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();
        }
    }

    println!("Done.");
    Ok(())
}

/// Convert BGR byte slice to u32 display buffer (0x00RRGGBB).