Function decode_mjpeg

rustcv-camera/src/decode.rs:93–123

(src: &[u8], mat: &mut Mat)

/// 将 MJPEG 数据解码为 BGR。
#[cfg(feature = "turbojpeg")]
fn decode_mjpeg(src: &[u8], mat: &mut Mat) -> Result<()> {
    use turbojpeg::{Decompressor, Image, PixelFormat as TJPixelFormat};

    // Create a decompressor. In a real hot loop, this should be reused
    // via the Camera struct. Here we create one as fallback.
    // 创建解压器。在实际的热循环中，应通过 Camera 结构体复用。
    // 这里作为回退创建一个。
    let mut decompressor = Decompressor::new()
        .map_err(|e| CameraError::DecodeError(format!("turbojpeg init: {}", e)))?;

    let header = decompressor
        .read_header(src)
        .map_err(|e| CameraError::DecodeError(format!("JPEG header: {}", e)))?;

    // Extract step before mutable borrow of mat.data to satisfy the borrow checker.
    // 在可变借用 mat.data 之前提取 step，以满足借用检查器。
    let pitch = mat.step();
    let image = Image {
        pixels: mat.data_mut(),
        width: header.width,
        pitch,
        height: header.height,
        format: TJPixelFormat::BGR,
    };

    decompressor
        .decompress(src, image)
        .map_err(|e| CameraError::DecodeError(format!("JPEG decompress: {}", e)))?;

    Ok(())
}

/// Fallback MJPEG decode using the `image` crate (pure Rust, slower).
/// 使用 `image` crate 的回退 MJPEG 解码（纯 Rust，较慢）。